No, just charge for the amount of storage they use on your server. Not the amount of data you think you’re storing. In non-special cases these will be the same number.
replyMakes sense.
replyWould there be any engineering/management pushback on the customer side? "we have to write a tiny script", "this is non-standard" / "why are you the only ones who charge us for filenames?"
(have limited knowledge here)