I'll repeat my own story again. Gloss over it if you're read it before.
I have a site that gets 160,000 to over 200,000 visitors a month, with 800,000 to over 1,000,000 page views per month. I have 1600 pages on the site.
In late 2005, a widget manufacturer approached me about putting banner ads on the 17 pages on my site that feature their products. I suggested we do a test for a month to see how many clicks they received.
After the test, we agreed on $600 per year for those 17 pages, which works out to about 11 cents per click.
For 2007, the advertiser wanted to be on 26 pages on the site, and offered $1200 for the year. I agreed.
The site is in a low-paying niche, though.
Six weeks ago, I launched a financial-related site. It hasn't started ranking yet, but I put Adsense ads on it anyway. Someone clicked on one of the ads, and I was paid $1.81.
What a difference a niche makes.