Are you referring to Cloudflare's R2 storage? If so, I'm not sure that's completely comparable as Backblaze has a huge focus on backup systems, not just cloud storage.
[Edit: didn't realize Backblaze has cloud storage, I still think of them as the cloud backup company.]
Backblaze offers "B2" storage, which is also API compatible with S3 (and cheaper, no ingress/egress, etc). I think their focus is more long term storage (slow, infrequent access but cheap per unit).
Backblaze B2 charges egress (at 1 cent/gb) with the exception of egress to bandwidth alliance members, B2 storage served via cloudflare is interesting because it means no egress charges, but unless you're just using it to serve normal webpages you're probably breaking cloudflares TOS.
I had a chat with Cloudflare about this, and you can use it for hosting downloadable files or really anything you want for personal or commercial. I had used it as the backend for my photo app with 10s of gigs of downloads per month (not a lot, but enough to prove it was free and CF was fine with it).
[Edit: didn't realize Backblaze has cloud storage, I still think of them as the cloud backup company.]