Here are some figures of actual viral video productions
http://newteevee.com/2007/11/07/master-viral-video-advertising-in-3-easy-steps/

There are well-known companies that do virals, but they are massively expensive
Here's one I'm not sure about, but they list their rates and their promise of 100,000 views
http://www.bytecaster.com/video-marketing/viral.aspx