If a user pays $10/mo and listens to nothing but indie streams, those indies are getting far less than $7.50 (more like pennies) due to the way they calculate their payouts. The major labels pocket the majority of that money.
Spotify have the ability to change this, but not the will to do so, because the major labels own a stake in them. Soundcloud recently launched a payment model that matches pretty much exactly what indies are asking Spotify to do, so we know it's possible but Spotify have been stonewalling indies about how it's too complicated for years.