Or are people paying $1K/mo (subsidized) just because AI is fun? Can you imagine a video game charging $1K/mo?
But you might have hit the nail on the head - yes, it's extremely fun and maybe that's the main reason after all. And FYI many, many people pay a lot more than $1k/m for video games.
In Tan's case, I think the "fun" thing is the right way to look at it. He gets to play at being a big shot developer and show off on Twitter, so clearly he feels he's getting some value from his spending even if no-one else does.
There is a more serious question about to what degree the AI vendors have a duty of care to prevent addicts from getting themselves into financial trouble - perhaps they might in future face the sort of regulation applied to high street bookmakers. I doubt Tan would fail any putative affordability test, though, so it would still be up to him to seek help for his problem if he feels its getting out of control.
It sounds like a lot when I type it like that, but it's not actually that much if you delegate brutally. Like I said, I'm constantly token starved and could do a lot more!