I'd like to suggest a guideline for food prices: Price = Energy gained when consumed.
I've noticed there's a lot of underselling going on in the auctions (I've done it too). I've read and been told that underselling (ie, charging less for an item than everyone else) is actually terrible for an economy, because it drives the prices down to the point that no profit can actually be made on it.
If we cooks got together and followed this (or any other profitable) guideline for food prices, I think we might all be happy to find we can actually make a profit at our chosen profession :)
(It might also encourage and maintain a wider variety of food on offer because different glitchens will have different budgets)