It's hard get any good profit to playtime ratio in TF2 these days... Do you play Second Life? I heard it consumes a lot of time from you if you want to be profit seeker...
Even though I'm not MMO player, I liked this post and included it in my Gaming's Daily because it's well organized and maybe my readers get something from.
By the way, being a game tester isn't playing a game... Most of time the tester job is looking for the bugs via certain methods, rather than playing normally until a bug comes up. It also includes playing the same part of the same level over and over. Yeah, that's not a job for everyone.
Yes, most of the search for bugs from the game, but it's just a side job. It's better to have a steady job than to do this without any definitive results.