I was thinking(try not to hurt yourself) a great way to have people spend massive amounts of gold is to obviously add gold sinks. Came up with a few ideas:
1. NPC that allows you to buy extra rune slots for skills
2. NPC that sells extra NV stacks allowing you to reach 10
3. NPC that sells a 2 hour buff that lets you swap skills without resetting your NV stacks
4. NPC that sells the ability to keep your NV stacks upon logging for up to 72 hours.
5. Casino
I remember when inflation became outrageous in Everquest they added an in game casino and people poured millions and millions of plat into it for chances at getting a rare ticket that would then give you a chance at a novelty item that no longer dropped in the game. And it worked prices on AH goods began dropping within the first week it was out. Sure eventually people began not playing as much but it had already done its job and removed a lot of plat from the game. Now this was many years ago and I havent played in a long time so Im sure inflation is back but the fact is for a decent amount of time, at least on my server, the gold sink did its job.