Assuming a 100% conversion rate and that number is accurate, 3.2 million a month or $38 a million a year.
https://www.theguardian.com/technology/2022/oct/31/elon-musk...
Just the notoriety of convincing Steven king to pay for a blue checkmark is worth outsized dollars to him and nothing to King.
When you pay 40 billion for something you expect a return on investment
Stephen King doesn't need Twitter to publicize his work, and he doesn't even need to work, since he seems to be quite well off. But most celebrities -- "most" is vague, I know -- live to be the center of attention, to be heard, to be considered. And a few years ago the platform was Facebook, then Twitter, after Trump's election, became more and more the place to be if you want to participate in the "discourse." King needs Twitter now or another platform now or in the future because, apparently, he needs to be heard, to be part of the conversation, to have his old man criticisms heard. But now that platform is Twitter.