I think of the same thing. At least for common items there can be limited prices. Absolutely unique items and pokemon may have price limits but it would be really high so that people can appreciate the uniqueness if they want.
edit: but if limited prices is reached once then the winner of the auction could be determined by still bidding but not increasing price. or some items like ordinary pokeballs would never included for auction in the first place. because limiting prices contradicts the idea of auction though.
