In order to find an answer to the question "Why not just use cloudflare?" for mirrors, I ran one of my mirrors on cloudflare for a week.
Attached are the results of the test. The week included a new release of tor browser, which generally creates some load on my mirror.
The results are that using cloudflare doesn't offload the binaries, which are what make up the bulk of traffic on the mirror. From past web log analysis, the vast majority of traffic is downloading binaries, as linked from 3rd party forums and sites around the world. It seems almost no one uses my mirrors to read documentation or look at anything else on the website. Cloudflare would be great if everyone wanted to look at the documentation or other html pages.
I've started to look at CDN providers to see if there are affordable services which can offload the entire site itself.
Constructive thoughts and pointers to CDN providers are welcome.