Here is an unpopular idea that would solve the problem facing GW2’s economy outlined here.
Pool the gold so that it’s directly deposited into the bank and tax it. For example, a player with 1000+ gold in the account accrue an estate fee at the rate of .5% per day. At 2000+ gold, the rate increases to 2% per day. At 5000+ gold, the rate would increase to 10% per day. This would encourage players to spend the gold and transfer their wealth to commodities.