Then you likely have at least the same amount of segments, if you used the default 64MiB segment (“chunk”) size. If you used something like 5MiB chunk size (the default for most of S3 tools), then if you have had files greater than 5MiB, the number of segments is greater.
In your case:
100GB / 532,000 = 0.192481203007519MiB
So, the average segment size is 0.19MiB, this is very inefficient, and will cost you
532,000/mo * $0.0000088 = $4.6816/mo
Thus I would recommend to use a backup tools like restic, Duplicacy, Duplicati, HashBackup, Kopia (but you need to disable Sharding), etc. instead of a simple copy.