My initial reaction was that running something like this is still a loss, because it probably costs you as much or more than it costs them in terms of both network bytes and CPU. But then I realised two things:

1. If they are using residential IPs, each byte of network bandwidth is probably costing them a lot more than it's costing you. Win.

2. More importantly, if this became a thing that a large fraction of all websites do, the economic incentive for AI scrapers would greatly shrink. (They don't care if 0.02% of their scraping is garbage; they care a lot if 80% is.) And the only move I think they would have in this arms race would be... to use an LLM to decide whether a page is garbage or not! And now the cost of scraping a page is really starting to increase for them, even if they only run a local LLM.