I just don't think it's any different now. Larger files, sure, but disc/tape space is bigger and cheaper, plus you've got cloud services like Amazon s3. Finding stuff, well, a cataloguing system can find stuff quickly even on drives that are stored offline.
Anyway, I can't recall encountering anyone who does charge like you're proposing, and wonder if small print on the invoice would be effective when the client comes back for an old image, but let's see what others say.