The music business is complicated.
I think this idea of recurring revenue is flawed. There’s potential that one could earn more from streams than a purchase, but that assumes the listener is going to stick around and not be swayed by the MILLIONS AND MILLIONS OF OTHER TRACKS that are on the services.
Also, has anybody done the math on how many times one person would need to listen to a 10-track album to make up a $10 sale (or a single track to make up a 99¢ download)? Must be something like hundreds of times. How many albums have you listened to HUNDREDS of times?