Why would you include the money required to pay shareholders, pay the humongous parts of the company doing ad tech, the lobbying money, the fine money, etc. What is the cost of running a social media site?
I have previously calculated that Mastodon costs including development are on the order of 1 EUR/person/year [1]. Even if you 10x it, it's nothing. Facebook does nothing more technically complicated than the forums of the 90s. It's just smarter design.
I am not. I am explicitly saying to offset revenue from ads. That's a different question. Best of luck getting Facebook-level distribution in your 1 EUR Mastodon.