From the CLI you can copy files to another bucket in another account owned by someone else within the same region without any bandwidth costs. You only pay for the copy requests. The copy request is $.01 per 1000 requests.
You could also create a lambda function that is triggered any time a file is copied with a certain key prefix (like a directory but not really), that copies to the other account. Of course you both have to set up permissions.
You could also create a lambda function that is triggered any time a file is copied with a certain key prefix (like a directory but not really), that copies to the other account. Of course you both have to set up permissions.
https://serverfault.com/questions/349460/how-to-move-files-b...