That’s not how Spotify works, though. According to the link above:

  Every time somebody listens to a song on Spotify it generates payments, but Spotify does not calculate royalties based upon a fixed “per play” rate.

Unless there are some secret deals being struck for fixed per-stream royalties that Spotify isn’t admitting to publicly, every rightsholder gets a percentage of monthly revenue. Which sounds fair, until you consider long-tail producers and consumers, for whom the marketplace is distorted by this model.

Your buffet analogy isn’t really apt here because streams aren’t limited resources, and they all have the same effective wholesale cost to Spotify (again, assuming no secret deals).