Quest you can only repeat once every x days.
NPC: Go out into the world and kill one of these many raid/dungeon boss/mini boss monsters on my list and come back to me with their head. Rewards a large amount of money toward your next charm.
-Reduces the amount of actual mindless farming you need to do.
-Gets people out to go kill shit instead of farming in a grind spot for cash.
-Still enforces a limit on how quickly players can farm up to the most powerful charms.
-Doesn't introduce a lot of extra platinum into the economy.
Aaand with that I'll get back to 3.0, sorry.