Okay, I think I need to check the forums more than twice a day.
Anyway, there isn't any real way to change the selling price of an item within a game.
You can, however, set it up a custom selling menu (just like the one with the scales, only you're selling them instead of making something with 'em). Each store would pay different prices for different items. You could also set it up the same way for buying stuff.
The idea is to set a variable = number of food items of a given type, then multiply that by whatever the buying/selling price is. Do any checks you need to do (such as when you're buying, compare the final price to your gold) and it shouldn't be too hard. I'll build another demo if you really need it.
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