Currently the Auction House (AH) charges a 10% fee based on the average of buyout and starting bid and there's a 10% tax upon sale of an item. (20% tax for best case scenario?!). This is much too high overall and the listing fee is badly designed.
It should be changed so that a 5% fee applies when the item is sold. For the listing fee, it should be 1% of the buyout price if one exists, otherwise it should be 1% of the starting bid. In either case the listing fee should never exceed 1000 crowns.
Edit: updated upon finding out new info.