Undercutters suck in 2.0, pure and simple.

How many times have you seen X put up an item for 150k gil, only to get undercut by Y who lists the same item for 140k gil? Now X comes back maybe an hour later, sees he was undercut, and adjusts the list price of his item accordingly, say to 135k. Y happens to be sitting at the market boards when this happens, and decides to drop his price once again as well, to 130k. After 2 or 3 days, the selling price of the item is now half of what it originally was.

Do you see what I'm getting at? I think it's insane that there are no penalties for this right now, and until there are, the extreme undercutting and market depreciation will continue to run rampant.

Why not simply require a small listing fee when posting an item on the boards (it doesn't have to be huge, say maybe 2%), and implement a tax whenever you pull an item from the boards before it's time is up (make this one ore significant to deter this activity, say 5-10% of the item's list price). This is just a suggestion based on what I've personally seen in previous MMO's that were successful at eradicating similar behavior.