One problem I think is that you can get these things from any type of shop. Knocking out teh "cheap item shop" doesnt exactly hurt you much in the long run.
That bit could be an issue.
There's a couple of other problems right now that may lead to changes as well, but I need more time testing them first. Let's just say, it's possible to get just a BIT totally overboard in terms of sheer power before the later parts of the game.