You should really double check your "very basic arithmetic", because it's wrong. If a user listens to fewer total songs than the average Spotify user, then the

You should really double check your "very basic arithmetic", because it's wrong. If a user listens to fewer total songs than the average Spotify user, then the artists they listen to will get a larger payout under a per-user model compared to an aggregated model, and the study I linked shows that this results in the top 10 artists earning ~12% less, which causes a larger distribution to smaller artists.