So - third world countries can't pay a subscription, and for USA its just not worth it because hardly anyone would pay $50+ a year to use Facebook.
Catch 22.
How about 2USD/year? WhatsApp ran on 1 until Facebook bought it.
I did the math at the time: with the users per server and separate user stats they were publishing, each employee could be paid very, very generously. Don't quote me on it but I think it was something like half or a quarter million per year. Yes, they were small and growing, as you grow you get more overhead as you try new things like eg. business customers or whatever, so maybe it can't be 1/year anymore (also because a decade of inflation happened in the meantime), but you can get very close to that or choose to operate in low and middle income countries at break-even or a small loss. I wouldn't find that unfair (as someone who earns in the top 1% of worldwide incomes, household income like 150k/year -- yes I'm looking into how to put that boatload to good use -- and who would be paying the compensatory high price).
Most probably estimates are that 5% of Android users ever paid. While a bigger possibly majority fraction paid $1 for the iPhone app.
It wasn’t sustainable.
AdGuard and Cloudflare (at least for Warp+) adjust their monthly and annual subscription rates based on location.
They can also do what companies like Steam and Netflix do, charge a differentiated fee by country. Some games which cost 20 US dollars might cost less than 2 US dollars in countries like Argentina (Steam)