I'm not sure why total volume really matters that much. A more relevant metric would be production cost compared to sale price. A music album costs about $15 at the most, and I would imagine that the biggest pop records only cost a few million dollars at the most. A new movie costs around the same, but a few million dollars is very cheap for a movie with a wide release. Of course, I could just be way off on my estimates of producing a major pop music album.