Is it really much different to how much artists got from radio?
Most artists never got radio money because it went into a label slush fund and was spent retaining the tent pole artists.
The big difference was radio wasn't on-demand. You couldn't just listen to a complete album. If you wanted to listen to your favorite artist, you couldn't do that on the radio without listening to a lot of other stuff.
The overall economics are wildly different.
Radio didn't pay much, but it was promotion for the album.
Spotify doesn't pay much, and it _replaces_ the album.