Inflation is a major problem, but drastically increasing existing goldsinks isn't the right way to fix it. For example, increasing repair costs by 10x and flight costs by 100x would be unfair to poor people. I posted the below in the 2 million gold mount thread too-- this is my solution to counteract WoD garrison gold inflation.
You create a vendor that sells three very cool, unique looking, bind-on-use mounts for 999,000 gold apiece and three bind-on-pickup color-variants of the same mounts for 100,000 gold apiece, then tell players that the mount vendor will be removed from the game on July 1.
People with "normal" amounts of gold will immediately buy the three 100k mounts, removing a large amount of their accumulated wealth from the economy.
People who borderline-exploited garrisons for gold like me, making many millions of gold, will also buy the three 100k mounts and then spend all their remaining gold on the 1 million gold mounts, because as they're being removed from the game, their value is sure to appreciate in the future. So the really rich players would remove all their gold from the economy too.
I believe this is the best way to outright fix gold inflation in WoW.