Also, while some pages may look like static HTML pages, they may be generated on the fly by an expensive and/or slow backend, which adds to the cost. I happen to maintain servers for academics and some content management systems are slow and have an expensive CPU cost. While it's OK for the low number of humans interested in the subjects they deal with, it's definitely not fit for massive bot scrapping. And before you ask, no, it's not always practical to have cache upfront or to pre-generate all pages.
The situation you are in is far less dire sounding when you consider that you have these options available to you.
It also depends on if you want your content to be scraped. Any bot ignoring robots.txt should be considered potentially malicious and worth considering such mechanisms for.
Also, if you are not using a big CDN (e.g. Cloudflare), you still need to pay for the traffic (even if you don't pay as much for the CPU). This is doubly true for smaller CDNs like Bunny.