From what I've heard, if your channel gets so many views, they'll pay you to advertise on your videos. The "What the Buck" guy has done interviews telling how he made his claim to fame through youtube, and he makes easily over 6 figures a year.

Shaycarl's main income is through youtube. Charles Trippy (CTFxC) too, but he sells shirts amoung other stuff. The Vloggers make a bit of money. Specially if you have cute kids like Shay Carl, lol.