I get your logic on this issue, but that's not exactly how currency works, and definately not how deflation happens, and I can see how the misconception leads you to derive your conclusion. Your proposal won't "fix" things as you've intended (if any, it might crash the market faster). The issue about listing fees and its shortfall and misconception has been discussed here:

http://forum.square-enix.com/ffxiv/t...taxes.../page2

Rampant undercutting brings the price of an item closer to its equilibrium price, and does not cause deflation. Deflation means general decrease in the price level of all goods, not just some of them. Thus undercutting happens, which reduce the price of an item, simply because there's an abundant of supply and little demand, period. Once it hits equilibrium or near it, undercutting slows down. Just look at the price of items in some heavily populated servers (Tonbery) and compare them to less populated servers (Malboro) and you'll see. If rampant undercutting consistently happens for an item, that simply means that item's price is not at equilibrium yet...otherwise it's just a short term thing.