Certainly Spotify has less staff per a station, but someone needs to keep the equipment running, ans I suspect more than one person is involved in programming their literally infinite stations, trying to keep the radio features, and the new music discovery better than that of Pandora, Google, and Beats. The app needs to be maintained and kept better than the others too. I could be wrong though, Wikipaedia says 1500 employees.
They are not one radio station, but infinite radio stations, and they need to negotiate for their music, in multiple jurisdictions.
The real problem they will have though, is that unlike radio, the [Spotify] stations are good enough that they replace owning a collection. Streaming services aren't a substitute for radio, they're a substitute for a music collection, and it's a business model that's having trouble taking off. Early systems were too restricted (both by technology of the time, and contracts) with too limited a selection, then came services that really work, but they provided it all for essentially free (less ads than real life radio). The internet streaming can't extract enough money to keep the labels happy, while simultaneously cutting into their sales. I don't know what the solution is, because people are going to be hard pressed to buy a track at a time when they had access to almost everything.
Nobody will pay Spotify to play this or that single, because Spotify won't generate sales for them.
I know I'm done buying CDs and tracks (I do pay for Google's service though), if they kill streaming, I'll be a pirate.