A while ago, I noticed some very small oscillations in my Cloudflare R2 bill (1-2 cents / month) and decided to ask about it out of curiosity. Support was tepid - understandable for my $1 / month account - and it wasn't until later that I realized the difference probably had to do with the number of days in the month.

Would this API have helped?

Translated: Close, but still not hard cost cap at Cloudflare.