The overall economics are wildly different.
replyRadio didn't pay much, but it was promotion for the album.
Spotify doesn't pay much, and it _replaces_ the album.
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.
replyMost artists didn't make money from album sales.
replyThey received some money up front in a contract to record the album, and the label make the money from sales.
There is a reason the bands toured and sold teeshirts.