I dont understand why a "tax" sounds good to the players? Usually, the developers would add in a pricing listing or such to create a money sink in the game, and a tax on ah might discourage new plays from putting items on ah. With chest shops Im more for, yet it could be the town that decides and when you make a chest shop the town gets a down payment for the shop, many shops nowadays are empty and it would be great to eliminate empty shops btw.
Thats my 5 cents on the matter =P