$50bn/year would be more revenue than fb had in 2017, though of course the majority of their 2.23bn monthly users would disappear if asked for $.01/mo.
It is an interesting thought experiment, though, to consider what facebook would look like if its revenue was derived from convincing users that it was worth a monthly subscription.
I remember when Facebook was still figuring itself out, back in the day, users could purchase digital gimmicks directly there, to send to other users. Some "pokes" or emojis or something like that,
I topped up my FB balance with like $2 or $5 dollars, in ?2006?. When Facebook (quickly) discontinued that silliness, my account silently disappeared. MARK ZUCKERBERG, YOU OWE ME MONEY!
Running Facebook would become much cheaper if they could focus on being a social network instead of being an ad selling business. Right now they have to do both.
I know the majority of people I know have at least 2 fb accounts. And then considering bots and other things. I'd imagine then that at least double your quoted amount per real human.
Which is bonkers to me personally considering how little I use it.