There is a few other things that could be used as a plat sink, which I agree should be discussed (especially if we want to keep the Casters Guild and Fighters guild quests the way they are).
Maybe a vendor selling CoTH stones with charges would be a good path. Maybe a single charge stone for 10k, and up to a 5 charge stone for 50k (or more, I myself am usually broke, but honestly I never find anything I want to buy anyways anymore. I would, however, buy CoTH stones like crazy!).
Maybe we can figure out a method of using PoEarthA as an extension to PoFire as a zone to EXP in. However, if it could be instanced, maybe you pay 5k per person to zone into your own PoEarth instance, and get to EXP in there for a limited time? Having an entire zone for yourself would be awesome for a little fee!
What about the alternate advancement AA that gave you bonus exp. I know hunter removed it because it was exploitable with RoA, but if instead we set up an NPC that would give you the buff for a price (10, 20, 30k? plat, useable once every 3 days?)
I could probably keep going for a while