ECPM per channel on large volume typically is 16cts.
So if you have multiple ad spots on a page you might increase that a bit but it's not like two adspots work out to 32 cents, the amount per spot goes down as the number of spots goes up.
I have some sites that do around 25 cents eCPM, most of the time I wouldn't bother with a eCPM that low... $1.50 or $2.50 is more like what I want.
I've got a project in the pipe that I'm projecting about $2000/month in ad revenue... That's based on an extrapolation from a series of smaller projects covering similar domains. Both my black hat SEO friends, legit "Web 2.0" people and people who are experts in this subject domain would all think I'm crazy, but that's exactly why I can pull this off... Nobody thinks this will work so ranking for this is like stealing candy from a baby.
Unfortunately, the average webmaster is drawn to low-eCPM topics like a moth to a flame... That's their loss.
So if you have multiple ad spots on a page you might increase that a bit but it's not like two adspots work out to 32 cents, the amount per spot goes down as the number of spots goes up.