Automated method of finding the correct price of something? It's called the stock market. But I do look forward to having an agent go out and search not just o

Automated method of finding the correct price of something? It's called the stock market. But I do look forward to having an agent go out and search not just on lowest price but some fitness function (% of being ripped off, chance of insane s/h fee's, etc) besides absolute price.