I have been trying to contact AWS and look for information in their own knowledge articles but haven't been successful.
I'm trying to figure out how the billing works for AWS Backup.
Let's say I have a 100gb bucket and I back it up daily with a retention of 31 days in region eu-central-1.
I then also create a copy job that moves the backup to a secondary vault in the region eu-north-1.
On the 1st day I pay the full price for copying 100gb from eu-central-1 to eu-north-1.
On the 2nd day I have added 10gb of data and made some modifications to existing files.
Will my copy job on the 2nd day be billed for a transfer of 110gb to eu-north-1 or only the delta(The 10gb + changes)?
So, to answer my own question. The copy job on the second day will only be billed for the extra data and not the full size.
I used AWS support as well as my own tests to confirm the result.