How much does it cost to advertise on Facebook?
It depends on the type of campaign you want to run. You can get more information on this page http://www.new.facebook.com/ads/?ref=pf
It depends on many factors: where you advertise (newspaper, tv, internet, etc.); how much you advertise (number of commercial placements for example), who you are advertising too (mass market vs. a specific small market segment); and what you are advertising (some things can't be advertised in all forums i.e. hard liquor)