I think a good idea would be to regulate prices for items in shops. This would keep sellers from making their items ridiculously over-priced. As I am typing this I'm realizing it's a bit of a stretch but not everything has to be priced. For example: only food items and blocks could have prices while shop owners could make up their own prices for things that are a little more difficult to determine their value such as enchanted armor and tools. Again, just a suggestion, this probably won't happen anyways.