I've seen so many attempts to justify this or that crazy thing in various fantasy RPG economies, but they don't tend to hold water as far as I've seen. I realize that suspension of disbelief is technically an option here, but my brain clenches up when I notice a lot of the most obvious problems.
For example, in Moldvay/Cook D&D (and Labyrinth Lord), a light footman mercenary earns 1-3 gp per month. That's enough to buy a backpack, if you save up for two months. Let's say that these are all extremely durable artisanal adventuring backpacks. The soldier can instead spend nothing for a month but 2gp for a sack. That 3 gp per month can't buy a week's rations. Presumably in Mystara, garlic is extremely rare: it goes for 5gp a clove.
These kinds of implausibilities abound in all the fantasy equipment lists I've seen. I think there are ways to justify some of them. The explanation I remember reading in some ancient D&D books in my youth related to massive inflation because of adventurers hauling unending gold from ubiquitous dungeons. If that's the case, though, wages should still make sense.
The 1E PHB happily includes some kinds of daily expenses, like 1 sp for a simple meal and 5 cp for a pint of small beer. A footman still earns only 1-2 gp, though, which makes it seem entirely untenable.
It seems like a coherent price list and wage list would be a great start to making a more plausible economy. (If I were making this online, I'd also include a slider to simulate recent booms due to dungeon hauls.) Has anyone produced a game or game supplement in which the economics of the fantasy world have been addressed with attention to detail without growing cumbersome and insane? I assume that most fantasy games' economic systems could be ported to one another.