It really depends on your site and what niche you're in. Charging a certain amount because of one specific metric should not be done, however, a lot of people mainly look at PR and DA.
Sponsored Posts can start at $20 and can reach 4 digits, the average (my experience) being in the window of $50 - $200 though.
Monetizing with sponsored posts is quite popular, you can either contact different companies/services in your niche and/or use some of the platforms like teliad, linkworth, payperpost, etc...