I see a few top WoW streamers making almost full time money with their Twitch streams.
However they are people from world first guilds, multiple 3v3 tournament wins or people that had huge YouTube audiences to begin with and moved to Twitch.
In addition to that the people donating are likely jockeying for lessons, carries, etc. It's very easy for guilds and players to say they are not doing paid carries, they are doing streams with subscribers.
However I am amazed that dumb chicks can do random BG's, farm fel iron show some side boob and have top donations over $1,000.
I will never underestimate just how completely stupid and desperate some gamers are.