Wow, so many people!
Firstly, as for the buildings, yes, I am aware that they're old Tevinter ruins and stuff. My point about building repairs is because they're old, naturally they're going to need repairs of =something= every year or so, just like a house (in fact, probably more than a house because these buildings are a gazillion times bigger than a house, made with ye olde materials, and Fereldan at least seemed very damp). Furthermore, that's not including the stuff that gets destroyed when one intrepid apprentice attempts to try out that "sweet looking" fireball spell s/he saw one of the enchanters using. How many rooms/walls get accidentally blown up per year and need to be replaced? Especially if the Circles are taking really young kids who don't know what they're doing. Furthermore, I would imagine that due to prejudice and stuff, the construction workers' union of Thedas would probably charge double what they usually charge because of the "danger" of being around mages.
Next, I =suppose= that I can believe that they get a bulk of their food from gardens within a circle, but they still have to supplement it with food from the outside--like meat for instance, and milk, cheese, bread etc. Unless they also happen to have cows, animals for slaughter and a place to refine grain into flour? But that's getting into a ridiculous amount of work, and I find it unlikely that mages would abandon their studies to milk cows at the crack of dawn. Or tranquil for that matter.
And I have to admit, I did not think about the lamps. The lamps were also mentioned in The Calling, I believe too, so good catch!
And yes, the lyrium! Dwarves have to mine the lyrium, so how much do they pay dwarves to go hunt around and mine it? Especially when the deep roads are full of dangers? And do mages/templars exchange lyrium pro bono or do the templars charge the mages per ounce of lyrium dust in order to help control how much they have access to? As to why you can find lyrium potions outside of the Circles, my guess would be escapees from the circle who stole supplies and smugglers who hijack shipments (like those bros that attack you in the undercity of DA 2).
Speculation is fun!