The key thing about almost any item in FFXiV is that they aren't very difficult to make or acquire yourself. Compared to "real" markets - where I'm going to find it pretty difficult to enter the car market, for instance. This means that if I want the item enough, and I don't like the market price, it's not going to take me long to obtain it myself. I think this acts as a great way of restricting prices to reasonable levels.