> unlike humans, their time is dirt cheap.

On the contrary I only want to visit a few pages on a given site and have an entire laptop at my disposal. Meanwhile for bots efficiency is key. A serious scraper (ie the type of actor that actually causes material problems for site operators) is performing tens or hundreds of pages loads per second per core spread across thousands of sites. Making a single page load take even half a second of cpu time is a massive win for the site operator.