How would this stop crawling by users who cannot afford the API subscription or don't want to pay for it?
I think your suggestion would reduce crawling, but not prevent or block it.
I think your suggestion would reduce crawling, but not prevent or block it.
I assume the people that can't afford it are using it for non-revenue generating purposes. I don't know that I'd care about those people if they aren't taking away from my bottom line.
You've gotta get that good yummy content publicly accessible for google though, so you'll rank. So, that's a balancing act.