How much they earn in AdSense is not half of the answer, it’s how much they spend every month which matters ultimately. Do they run AdWords ads to get traffic? How much do they have to pay each month for their web hosting solution? How many websites and hours of work every day do they have to do for which ultimate net income?

The list might not be the same as pure adsense earnings.

If I pay a million dollars every months to adwords to bring traffic to my site, maybe I’ll get half a million dollars back in adsense, if I’m very unlucky. So I’ll be loosing half a million dollars a month but still would be at the top of this list.