It should be easy to calculate this for your own needs based on your playlists. The advantage of buying is that you build up your own catalog of artists that you listen to regularly which means you don’t have to keep paying for them. So, at first, buying the albums would be more expensive but after a few years it would become much less expensive. The exception would be if you are always looking for the latest tracks by a large number of artists but I don’t think that’s most people.

Older popular music can be purchased second hand or as a various artists album which also saves money.