[vanilla_nut]

Average revenue per user is $70/year in the EU and $230 in the US. But how much of that is profit? How to costs compare between serving a user ads and serving an ad-free user?

Server costs for images, text, and the occasional video can't be that high per user at Facebook's scale of billions.

But costs for the Rube Goldberg machine of ad hosting, recommendations, bidding, and serving? There's a whole lot of backend infra and middleware behind that. We should assume, at the very least, that ad-free users are cheaper for Facebook (unless they go through all of the backend recommendation processes for all users but simply hide ads from ad-free users). I assume that with some optimization ad-free users ought to be significantly cheaper to serve.

[fallingknife]

The backend cost per user is going to be about the same for a user anywhere in the world. So we can set an upper bound on the cost at the level of revenue per user in the market that generated the least revenue per user. That's going to scale with GDP per capita, so I feel safe saying that there are many markets where they get less than $10 per user per year, and therefore their marginal cost per user is less than that.