While a agree that cheap items exist and there is a build up of them during the 5-6 centuries of Order existence, the same rule than for rituals applies: if it can be done through mundane means, why would a mage waste time and resources to do it by magic (even the cheapest of magical item cost a pawn) ?
Magic lights are useful, cheap, but really only needed: in close space where suffocation could be an issue or to reduce fire hazard (library). A dozen of magical candles still requires a dozen of pawns and at least a season of work - a Verditius would charge 12 pawns, plus twice the amount of vis he extract in a season (let's say 5, on the small side) so a total of 22 pawns for a dozen of candles... suddenly it is not so cheap.
Lamp without Flame, Base 4, D: Sun (+2), T: Ind, R: Self, 1 use a day (+0), without env. trigger to make it as cheap as possible, is still a level 10 enchantment. Assuming a labtext available, for a dozen to be done within a season, a mage would still need a lab total of 120... Nope. I don't see the Flambeau Archmage doing that. More reasonably, a labtot of 60, to make 6 candles a season, by a moderately specialised mage.
It is a good exercise for a apprentice as a first enchantment, but it still cost one pawn, whereas torches are cheap to manufacture, lamp oil requires... oil only. Candles requires a bit more skill to manufacture, but how many can you buy with the cost of one pawn - and at one stage the covenant will likely have it's source of light, whether it is oil or candle.
So yes, it is sexy to imagine a covenant with lights like Hogwarts, and some covenants will looks like that, but they are not the majority.
Finally, like most simulation done (for book level and quality existence, for mage's age, etc...) it depends on so many parameters that's the variance will always be very wide.
I would also easily imagine that with the exception of House Tremere organization of tracking magical resources systematically, most covenant would loose track of minor items given to grogs: where is stored the stone cutting knife used while building and expanding the covenant ? And the Glove of the Carpenter we used until we were able to hire a good mundane specialist ? Those items had their used, were looked after while they were needed, but slowly, after one decade of not being used might have been forgotten and are not missed by anybody. Then maybe a grog found it and trade it, possibly to somebody outside the Order.
The idea of cheap items trade is sound (and a good source of grog adventures), as covenants tied up for specialists or resources would look for such answers, but I would not see ten of thousands of items stored left and right amongst the Order.