But my cable/Hulu/Netflix streaming bill isn't where Fox's revenue comes from - it comes from their advertisers. If they sell me their shows in a convenient .avi format, they're gaining me at $10/month, but they're losing every single company that pays for me to watch their commercials.
This means each user is worth $0.01 per minute of commercials. The average American watches ~4 hours per day, 25% of which is commercial advertising, which comes out to 30 hours per month of commercials. That's 1800 minutes of commercials.
Answer: $18/month, average. Roughly.
And then CPM for online video like Hulu is totally different as well - due to a number of factors, such as the smaller number of spots, the difference in attention paid, the quirks of Nielsen ratings on the web, and the clickthru opportunity.
There was some hubbub a while back about how CPMs for a 30s spot in the Simpsons on Hulu was actually going for more than a new episode of the Simpsons on Fox (something like $60 vs $30).
Most of the TV you watch on Hulu is prime content and even though it is online, you can expect a CPM of $25-50.