Hopefully this hasn't been posted already, but I found an interesting article on the BBC regarding Gold buying in Online Games.
It doesn't mention Joymax or SRO at all (hence why I didn't put it in GD!) but I guess the reason for that is it only mentions companies that are trying to stop it!
I don't know what the state of Gold buying is like in other games, so I can't really comment, but I thought some people may like to have a read, particularly where the monetary figures are concerned.
Click away:
http://news.bbc.co.uk/1/hi/technology/7226818.stm