You aren't buying a door. You are performing a piece of someone else's work for a period of time, for a given audience.
Artists don't necessarily want to be paid over and over again for the same work; however the economic value of an artist's work can only be established by how many people are exposed to the performance. Therefore, the only fair way to reward a songwriter is to pay him/her a little every time the song is performed under certain circumstances. The more performances, the more important it must be, and thus, more reward to the people who made it happen.... theoretically.
Not true. I buy a CD, and I don't have to pay (yet) the artist an additional fee every time I listen to it, or, for that matter, how many people I have in the car with me. OK... Maybe I'll grant that the only reason I don't have to pay more is because they haven't figured out a way to enforce that (yet)...
In the final analysis, I'm also suspicious that this is all a huge red herring. All of the people that I know that download lots of music as MP3's ALSO have enormous CD collections and have bought copies of just about everything they download. They're into music. They buy music. They download music. Big hairy deal.
I have had many titles on vinyl. I've gone out and bought much of it on CD's to supplant the old vinyl records. But: If I already own the recording, couldn't I download it from the Internet for listening in another format? Do I have to pay for it again as an MP3?