I did some like-for-like comparisons across S3 vendors. S3 perf is way better than the challengers, R2 is the worst performer. Also it doesn't support concurrency on list operations, or object versions.
So it's a bit more complex than "R2 is best coz it's cheapest" it's not super optimized yet
https://twitter.com/tomlarkworthy/status/1711846776905293967...