There is no labor in making digital copies.
You are trying to blur the line between the media/art/music/film, etc, and the reproductions of it.
Artists do deserve to be paid for their work, but artists do not deserve to maintain ownership over the already-sold assets, nor whatever happens to those assets afterwards (like copies made). If you want to say they should retain commercial rights for reproduction of it, sure, but resell of the originally-sold work (e.g. the mp3 file), and non-commercial reproductions from that sold work? Nah.
They didn't put in labor towards that. To say they did expands "labor" far beyond any reasonable definition.