It is often the case, as I run my stories, that I'm left wondering "How much should this NPC ask for a certain item or service that the PCs are trying to acquire?" - or the symmetric question "This NPC wants something the PCs have - how much is a reasonable offer?". Sometimes the amount is set by dramatic needs - a neighboring covenant will give the PCs a certain book if they embark on a certain mission I have planned for them. But sometimes I have no clue, and I do not want to turn the acquisition/sale into a story - just to come up with a "realistic" exchange.
I think the best way to gauge the "hermetic market price" of something, is just to ask you, fellow forumites: how much would your PCs be willing sell a certain item/service for, or how much would they be willing to pay for it? Let me make it clear - I am not asking how much you think a Quality 11 Tractatus on Vim is worth, but how much your own covenant would be willing to pay for it, if your PCs would be interested in it at all.
Thus, I am starting this thread in this spirit: anyone can post here hermetic items sought or on sale. Other forumites, if their current or past covenant would be, or would have been, interested in the trade, respond with a price (not necessarily in Vis - perhaps seasons of service, books, Tribunal votes etc.). The offer and/or answers may be in character, but what is essential is that the description contains all necessary information. For example, in case of a book, in addition to basic Quality and possibly level, any bonuses/penalties (e.g. resonant materials, damage etc.), whether it can be freely copied/redistributed or not, whether it can be loaned etc. In the case of a magical item, it would be interesting to see how much it would cost to the maker in terms of vis and labor, not just the final result. Thus, out of character talk is probably easier.
Assume that everything happens in a perfect information environment - there's no cheating, hidden hooks etc.