Well I used to make much more, years ago, and now it's down to just over $100 per month. It's been declining due to a combination of reducing rankings of old pages and getting the junk Ads on my high traffic pages.
The low traffic pages do get some nice payouts though, I guess it's because that traffic is super-targeted?
But, I am really grateful for being able to simply cut and paste code to my site and get paid for clicks. And it covers all my hosting costs easily.