Obviously not a lot of people who studied economics in here. First off, anyone who says that adding a sales history is going to mess up the economy doesn't understand the concept of supply and demand. The reason prices rise is there is higher demand than supply and the reason prices fall is because there is higher supply than demand. It has absolutely jack to do with sales history. Also there are already ways to figure out average and median prices (YG) and also you can see all the prices posted using the search feature in the wards.

As for the fees, SE has to take money out of the economy somehow in order to combat inflation. The money that you get from leves, missions, quests w/e comes basically out of the void. If there are no fees, like those for choco rental, AH post fees, ward taxes, then eventually the prices in demand items will inflate drastically. Items which like gil, come out of the void commonly will be more immune to the inflation, but items that are more rare (like the Kraken Club in 11 which at one point was going for 900 million gil on Remora) will skyrocket in price.