I read somewhere TechCrunch generates $214,000 per month from advertising.
One of my sites has around 1,000 visitors a day, generates $5k-$10k revenue a month.
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/10/21/...
http://www.techcrunch.com/advertise/
He also has quite a few other ads running as well. He's making an incredible amount of money and has been for years now. Selling your own ad space is by far the most profitable way to make ad money.