If you had to pay the tax when putting an item for sale then we'd have more stable economy.

The thing that might happen though is that all those cheap items wouldn't be worth selling anymore.

I'm sitting on 2mil I made off mb alone so for me the system is working just fine （＾＿＾）☆
The gil is almost useless though so I don't see a reason to be all up in arms about it either way.