> That costs the crawler money

They're for-profit operations. They have money, and it doesn't cost that much. Proof of work is significantly more expensive (but then you put delays on even the users in your own region).

> banning country and AS numbers for cloud companies is pretty effective in my experience

It's the sort of thing that works when the first person initially rolls it out because the crawlers only bother to do something about it once a threshold percentage of people are doing it, at which point they use the workaround.

And then you have people insisting that it works even though it only used to work, and meanwhile you're still blocking actual humans.