[at0mic22]

It's not exactly true. You don't need to solve the challenge per each request as PoW systems provide you with a session token which is valid for a while.

Basically you need session-token generators which usually are automated headless browsers.

Another not-exactly-valid point is you don't need a botnet. You can scrape at scale with 1 machine using proxies. Proxies are dirt cheap.

So basically you generate a session for a proxy IP and scrape as long as the token is valid. No botnets, no magic, nada. Just business.