Going by the title: what's to stop people from paying the $1, and then let a bot take the wheel & do everything bots were doing before?

Only temporary ofcourse, until the "pay $1 & proof you're human" is automated too.

$1 To replace a human (account) isn't that expensive for say, a propaganda campaign, is it?

If I disambiguate from Musk running the show, this is not a bad idea. When I was working on payment gateways a good 10 years ago, it was stupidly hard to get live cards accepted for live testing. (Because of course the test API was different.) At some point all our test cards would be blocked based on the transaction volume.

I hope they're doing this to spin up a massive human call center, which would displace a lot of those jobs about to be replaced. It should be the only source of payment.

With the advent of AI it's becoming more and more expensive to be human. By 2030 humans will pay everywhere to prove they are not bots.

How does one prove the other? Companies already have the same rights as a human, and bots are heading in the same direction