We ran an ad, recently, on Facebook using the CPM method paying for the number of views.  Our ad was run for a day to Seattle area facebook users within the 21-45 year old age range. We had a budget of $50 and bid the recommended bid. 

As the graph shows, we had 14 clicks averaging $3.57/click. 

A note of caution: If you're looking to buy an ad, don't expect to see your ad run as with newspapers though. Facebook assured us that our ad ran and if you have Google analytics, you can validate that your ad ran.