Presumably, licenses to stream this music were acquired by Spotify from the artists' designated representatives. Presumably, too, those representatives are receiving some proportion of these licensing fees. If the deal is acceptable to the representatives but clearly abysmal to the artists, I wonder what percentage of the fees are being exacted by the middlers.
I know the amount of money received by a typical artist with a typical contract on the typical sale of a typical CD is, typically, very small.