It's all about your CPM, or how much money you get per view. Some youtubers get into a larger organisation such as machinima, some stay solo. Some people get as much as 3$ per 1k viewers, some won't even get a fraction of that. It all depends about the advertisers and your content. That swifty channel that you linked is one of the biggest and longest youtubers/streamers for WoW, and he makes 100,000's of dollars.

Killing galeon solo as a boxer might get some attention, but frankly no one will give a shit. You might get a few k views, heck maybe even 50k views, and all you will be able to do is buy a pack of cigarettes and maybe a beer with the profit.

If _you_ want to start making money, then your best bet is to stream with a webcam on, sitting in your leather hot pants and have some half naked chicks dancing behind you. And release some videos on youtube.