Understand S3 cost at folder level

I am planning for a use case wherein which my S3 bucket is used by 10 different users. All these users has separate folders within this bucket, to where they'll store their files. Now I want to know how much storage (and there by the cost) does each of these users use . I know there's cost allocation tag, but that's to be used at the bucket level. Is there anyway that I can get to know this cost, maybe using lambda script or any other way? Any help would really be appreciated.