As mentioned elsewhere in this thread, I think spotify have positioned themselves exactly to be in this situation. If they earn more money, the music labels still have all the negotiating power and will just take it, and if they raise their prices, less subscribers.

At a guess, I think spotify are trying to squeeze themselves into a position where the labels need spotify because otherwise artists just will not have the same reach otherwise, I know I dont listen to a band until they put their stuff on spotify. I have seen labels + bands be more reactive to making sure their stuff hits spotify quickly which seems to show a shift in power, hopefully the trend continues.