According to an article in Adweek, the value of a Facebook fan is $3.60. Vitrue, a social media specialist agency determined that a fan base of 1 million is equal to $3.6 million in equivalent media over a year.
Vitrue analyzed Facebook data from its clients – and found that marketers posting twice daily can expect ~60 million impressions per month through their news feed (not uniques).
With a $5 CPM, 1 million fans generate about $300,000 in media value each month.