You miss the point, which is: scarcity. There's only need to barter if there is not enough to go around for everyone. This has traditionally always been the case, but there's no guarantee this will always be the case. As I mentioned, it is no longer true for the music industry. There is no longer a need to count the number of copies of a song that exist - anybody can make more with no significant cost. All of society is built around scarcity, and with it gone, the music industry is about to collapse.