While i think your idea of having a bell-price changing function is a good one, I don't see why there should be any reason to restrict the price. If you are using Toolkit, you can generate all the bells you want, so what would be the point of altering the price to actually make money. it would be more so that people could come to the town and sell turnips at that high price just for the heck of it. And why not? A restriction on the price just seems unnecessary to me.