Look, basic economy lesson for you:

There is money in the game. You need money for all sorts of things, not just flying mounts. Potions, regents, enchants.. whatever.

If people have lots of money, inflation will make normal items cost more. So a potion of healing will cost more if there is lots of money in the system, rather then if it's a small amount.

If people end up getting to level 80 and have nothing to dump there cashflow into, potions and other normal AH stuff will skyrocket, since they can be sold for a outrages amount without any problem, since a large majority of players have that sort of cash. This will end up in a server economy crash, where a small part of the server has huge amounts of gold, and the other parts have little or no gold.

Having a gold drain at endgame balances out the system, so that people who have lots of money get a item that has no real value besides looks and speed and people with little money can still buy the needed items for there professions at a price that is not outrages.

There is no way to remove this system, unless you put in a whole new economic system where gold, for AH activities repairs and everything gold related, is replaced by another thing.