Awful to see our personal privacy and social lives being ransomed like this. €10 seems like a price gouge for a social media site, and I’m even seeing a price tag of 150SEK (~€15) In Sweden.
However, when your platform is for everyone, does everything, hosts any kind of content, you have nothing to use.
Why can’t you use the content of the page to decide what ads to show? If there’s a Reddit thread discussing games, show gaming ads in that thread and kitchen ads in the threads about cooking. If your front page on Twitter happens to have multiple people writing about traveling, show travel ads. You don’t need to know anything about the users to advertise based on content.