I think the amount of revenue generated per user is considerably more than anyone would pay.

And considerably more than it would cost per user to host and maintain the service.

What the fuck?

There should be a payment to me set by me for seeing an ad.

In general, an ad is an attempt to modify my behaviour in the future and I suffer damage by seeing it. My fair compensation €5 per ad. If you don't consider me worth of €5 of business you have to filter me out of your advertisements. If you still show me an ad, I expect a deposit for each impression. Or I would in a perfect world..

Yes, it is possible to argue that users of Facebook are de facto unpaid employees. They produce the data that then Facebook sells, but does not pay any salary. It would be interesting to see Facebook getting Ubered.