I need info on [Income from ads] : [Number of blog hits/sessions] ratio in
the US blogging market (e.g. 50$/20,000 sessions/month).

PLS NOTE:

1. I mean income for the bloggers themselves, and not to the blogs
platform company (i.e. how much income a blogger can get from the blog
as function of the blog traffic)

2. The source must be reliable - one blog wouldn't be enough (:

Thanks, Eliahu

See this post : http://www.problogger.net/archives/2005/12/19/adsense-earnings-for-november-poll-results/
As an update (a year later) I would say that the ones who earn the
less are more numerous and the ones who earn the more earn even more.

Aslo, for AdSense you earn around 1$ per 100 visitors.