In what system could they make it so you couldn't check prices before selling your wares. People have to be able to check prices before purchasing an item. Even if you couldn't check the price while posting sales, the retainers are mere steps away from the market boards. People will still undercut. Adding a step or two between won't do much imo.

This real issue right now is server population, and the markets getting flooded with product. Crafting is still the only real way to obtain gil.