Earlier quoted context omitted.
You can't afford to pay them the amount they make from the ads you see/click. UPDATE: 2016 revenue is $27B. At 2B MAUs, that's a little more than $1/mo. Hmm. Surely there's something I'm overlooking.
It's not a matter of simple price per user. At its core, their product is the incredibly precise and nuanced network they have constructed though their various sources of user data. The value they get per click/view is only so valuable because companies are willing to pay for the quality of targeted advertising that only a company on the scale of facebook can provide. This model allows FB to keep their platform free…
It pretty much is when the question is about what the price would be for an ad-free subscription. The calculation may be more complicated, but it's all in service of a per-user number.