Page 68 of City & Guild has a nice chart for a few items to determine how many can be made in a season. Does anyone have an expanded list? Or can tell me where to find one? Or even better, is there a practical way to calculate it for other things?
For example: How many breads can you bake? Or how many arrows? Or herbal medicine? Or barrels of beer? (there is an entry for barrels, but not for contents)
I would appreciate views on how to make bulk crafting less subjective 
I haven't seen one. I doubt we can establish a practical way to calculate one that would work for all crafts.
My suggestion would be that a competent craftman or professionnal (Ability 5) can make enough items to sustain himself and his family with the equivalent of 2 seasons of work, with a little to spare. So the amount he can produce in a day or week or month depends on what that item is worth. (That is of course after his costs of production are figured in -- raw materials, tools and work place need to be paid too.)
So how much bread is that for a baker? I don't know, because I'm not a baker. But if I had to guess, I'd say anywhere between one and five hundred loaves of bread in a day. But it is as much a matter of his customer base than his physical ability to make bread. If you make too much bread and it doesn't sell, you are eating into your profits (pun intended) by wasting raw materials and fuel. If you don't make enough, your potential customer go elsewhere and may not return the next day.
There is a lot more to making a living through Craft than just making the product. Pricing it right, marketing it, retaining customers, supply chain, working environment. The list goes on and on.
Each craft has its own challenges. I only know a few, most from a modern and a few from a medieval one.
Another thing to take into account is that most craftsman don't do the whole job. He'd have assistants doing specialized jobs, as well as other craftsmen in town producing specialized items. Arrowmaking, for example, can be broken down accross several crafts or people doing some work. Shafting requires harvesting the correct kind of wood, then drying it, splitting it, smoothing the shaft and finishing it (to avoid warping). A nock needs to be either carved into the shaft or made from horn and glued. For fletching, the correct feathers need to be collected, sorted, split, then attached (with glued and thread). Arrowheads need to be made by a blacksmith before beeing attached with glue and twine, sometimes with rivets as well.
And almost everything is done by hand, so it takes a long time. A modern arrowmaker may assemble several dozen arrows in an hour, but he is using pre-prepared materials (shafts, feathers, nocks and heads). A medieval arrowmaker using manual tools and unfinished materials would take a day to produce the same amount if working alone.
You make a lot of good points to consider. In our saga, there are a couple of companions who have craft skills and it would be good to come to some sort of balanced perspective on what they are able to do with their crafting abilities when not out adventuring. And of course, what they might be able to achieve without having other craftsmen to lean on for support. On the other hand, they do have access to magi who could possibly help with some of the more tedious chores. So this would not necessarily be to make profit, but rather impact on what the covenant ultimately have access to (without having specialist grogs cause some players made companions who also happen to have high craft skills) and how much of it.
For me it is about finding a balance between player enjoyment and having a way to deal with it using the game system. Would love to hear more insights on this!
I struggle to imagine where these numbers would be relevant.
The productions of the covenfolk is the domain of costs and cost savings in the Covenants rules. So many different activities feed into the finances, that the production of one particular craftsman is not going to have significant impact. The same is true for an independent craftsman, whose activity is accounted in labour points.
An additional reason why detailed accounting is pointless is the massive difference between the capacity available in a crisis and the capacity sustainable over time. For instance, a war could prompt people to work 15-18h days seven days a week, but when the need is not overhanging, both health and common morals would forbid it.
Yes, I agree that neither Covenants finances nor labour points are particularly good systems, but I don't think low-level details is going to solve anything.
The issue we run into are along the lines of:
An very skilled companion spends the winter making arrows (+2) with a craft total of 19 the wood (shafts) and bodkins (Arrow heads) are not an issue.
So how do we quantify this?
Also Mythic Carpenter can let the caster do a month of work in a few seconds, 3 castings is a season's stock.
Hiring or raising a few traders to go to other villages and cities with wagons of goods shouldn't be an issue.
Are you shooting so much that he conceivable does not meet the demand?
I can see your point if the point is producing superior quality items for you own on-stage uses, and need to know if you enough for the story, but is it a significant risk? Would it be a gross error to assume that they produce all you can use?
Compare this to existing Covenants rules. There are lab virtues which require super-skilled craftsmen, but no limit on the number of labs one craftsman can serve. Similarly, scribing capacity is regulated, but the binders and illuminators under Covenants rules are not. The canon rule is `wing it'.
That feels like more of a problem, and it came up in our saga as well. How much silver can a magic generate/save using craft magic. I was very reluctant to allow significant income therefrom. While my motivation is mainly the fear of free lunches, there are several arguments which make it difficult. There is a lot of costly logistics to manage the supply chain which eat into the profit. Secondly (assuming sufficient supply of raw materials) the magus can produce more than he can sell.
This is not to say that I do not think some profit can be made, more that it is not enough to matter with the typical turn-over of a covenant.
Craft Magic
Craft magic hits one of the main differences between modern and medieval economy and trade. Today, labour is expensive while raw materials and transportation are cheap. In the medieval times, labour was cheap while raw materials and transportation are either costly or regulated.
Craft magic reduces the cost of labour and increase th speed of production, but at the cost of a higher waste of raw materials due to a failure of the Finesse roll. This means that, in the end, the profit balance should probably move only a little towards increasing profits. But since that comes at the cost of the mage's time (the most expensive kind of labour there is) and risk (from a Finesse botch), it should not not be a major issue. It just adds color to a covenant of magi with fewer mundanes. And some of their fellow magi may look down on them because of it, because they are "so poor that they need to use magic for something mundanes could do".
Production
In general, I would say that a craftsperson working full time (3 seasons a year) is able to pretty much fill the demand for a small community (20 to 100) for general day-to-day items (like food or furniture), for a group (5-20) of specialized users (arrows for hunters or archers) or for a small number (1-5) of individual with highly specialized needs (glassware for the lab of magi).
Trade
Trade is a highly complex issue. Most communities already have the craftspeople who fill the needs of their community. Sure, a few items are brought in by traders, but usually for items that cannot be produced locally. Those items are usually either bulk items (mostly raw materials for local craftspeople) or expensive (thus with a small market).
Introducing a new trader into the system usually upsets a delicate equilibrium. That is one of the reasons for the formation of guilds, for they provide previsibility in the market. The new trader can upset that. A guild's charter (i.e. the rule of the local lord) often have rules that forbid the sale of guild items by traders bringing in such items from foreign sources. The local authorities can also frown at the sale of some items (weapons) to the general public. They may also tax foreign luxury items heavily.
And each town constitute a fairly small market for the "magically-industrial" produced items. So your trader has to hop from one town to another to sell your items, facing slightly different difficulties each time.
Let's not also forget that there is a ruling in many Tribunals that limits the magical creation of wealth (see HoH:TL p.87, last paragraph of the boxed insert) to about 2 pounds of silver per mage per year. Should a covenant go overboard, this may result in their Tribunal sanctioning it.
While I agree with this in principle, it misses a good chunk of craft magic. Consider A Spell to Milk Cattle. Sure, this is just labor-saving. But now use craft magic similarly elsewhere. For example, mine minerals from the earth. Now you can increase the raw materials available, too.
If you use a few other spells, like CrAn or CrHe to grow things in a day, you can do similarly with non-mined stuff, though these aren't technically craft magic.
Creo magics still fall within the "magical creation of wealth" and, if overdone, can draw the attention of your Tribunal (or your mundane neighbours).
But the overall points are that:
No.3 can be something like "Ok, your covenant is using some of your Craft spells to improve the covenant's finances. For each 10 pounds of silver you add this way to your finances, one of the magi needs to substract 1 xp at some point during the year to represent the time he spents casting the spells, overseeing the production, blah, blah blah. If you want to avoid that cost but make that improvement permanent, spend the time and vis to enchant an item"
Such a ruling (of a variant thereof with a different cost negociated with the troupe), while purely arbitrary, helps keep things reasonable and prevent abuse. It can also provide a story hook at some point (a nosy trader tries to find out how you were able to push him out of a certain market, a noble wants to increase your taxes, someone steal the enchanted item, a rival covenant raise a complaint at Tribunal for creating too much magical wealth).
Mining does not actually produce raw materials. You can only mine what is there, so you are still only saving labour. Maybe a lot of labour, but still.
Obviously, the magus can generate a lot of wealth through craft magic and related spells, if he studies a range of spells to engage in every step of the supply chain, but then it is no longer a question of negligible time to administer one critical spell. Instead he needs to cast many spells, each at the right time and place, and then that's his activity for the season. No free lunch there.
Only if you're selling them, and Rego magics could potentially fall into this category, too. It's still magical creation of wealth. But you can supply tons of stuff for the covenant itself, keeping costs down dramatically.
From a point of view of physical science, yes. From a point of view of economics, it's usually labeled differently. Look at resources today. We have resources we did not count as resources years ago. But then we learned new ways to extract materials from the earth and they are now considered resources.
From a practical standpoint, you're just agreeing with me. My point was that overlooking the costly part of raw materials is a mistake because it, too, could be handled with labor-saving magics as well. Craft magic can reduce all of these costs. Even if the raw materials aren't local, Rego magics can still handle that well.
It is not clear to me if you try to imply a free lunch or not, @callen .
If you are, I disagree, by the argument in the rest of my post.
If not, yes, we agree.
But even if you are just supplying stuff to the covenant, you have to be careful how you do it. If you are showing everyone who visits a vast increase of wealth without a source for that wealth, you can draw the attention of mundanes.
Of course, if your covenant is not accessible to mundane visitors, the point is moot.
This community is amazing 
My key takeout is not to sweat the small stuff if it is not being used to unbalance the covenant or the 'surrounding economy' and I absolutely love the idea of the magi participation adding more flavour to whatever is being crafted/exhumed/other in the area. I also see a lot of potential story hooks this could create. I am a lot more comfortable if the crafting is done to enrich either the story or story potential and not simply for the sake of 'I can make all the stuff I need'/free lunch.
No, I'm not implying that. There is still effort to be made. Now, there are different ways to go about it. You could have a single grog with a great Finesse Ability handle nearly everything, but then you have to make all the items for the grog to use. (I did that once with some NPCs.) You could have the magi do it, but eventually there will be probably be botches or they'll spend time making Formulaic spells; and it will take some time out of their schedules, which may be often (e.g. cooking) or rare (e.g. making weapons).
The point is that you should be able to bring costs down dramatically without having to sell magically generated wealth. There are huge limits because you're only reducing costs. But that can be a ton that doesn't have to be brought in another way.
Just having to invent the spell to get a significant income at negligible casting time is a little too close to a free lunch for my taste. At least I would like to see the casting time counted in days before the income is made significant, whether the time is actually casting enough times or organising with the rest of the supply chain to cast it at the right time and place. But there is still plenty that can be done.