Hah I wish we could ignore them. It seems to just vary from ISP to ISP in the US but our small town ISP turns off your connection and puts you behind a captive portal forcing you to click through and accept what you did wrong before your connection is turned back on.
Either that or charging a micro transaction for loading the page. But yeah the goal is to make it cost a small amount that is insignificant to a regular user but adds up to a huge amount at the scale of a spam farm. And it’s also the same rationale behind hashing passwords with multiple rounds. It adds a tiny lag when you log in correctly but adds an insane amount of work if you’re checking every phrase in a password cracking dictionary using an offline attack because it adds up. (In the online scenario you just block them after a few attempts)