Just a bit of suggestion here. You could make donation system with goals/achievements. What I mean is that if there are for example mounts for 10€ or anything else. Completing a goal of 50€ will give you something else. Next goal is 75,100,150,200€ probably it should be capped or if not capped you should consider account wide options for these perks and probably non-soulbond items just to populate the auction houses :)
Regards,
Shock :)