The UO economy was crazy, for a while I had a 11x14 inside of Luna Walls and was making like 30m a week. Selling to a gold dealer using my friends paypal (I didn't even have a bank account at the time, I was in middle school and said friend was in HS). I was making just shy of a grand a month in 8th grade running a mall in a video game.
I later sold my account and the in-game land for 5k, I regret it to this day :(
What am I doing now you might ask...
Bitcoin :)