I'm a little confused. I see the value in the intended gold sink for the game economy, but what possible incentive would somehow have to donate thier refund if they ended up getting a house anyway? I think you gotta offer the players something or they just won't bother.

I think even something as simple as exclusive title like "Generous Donator" would be enough for people, though. (I think mounts or pets would be a bad idea, since people get really irate about pets or mounts that are super exclusive and impossible to ever get.)