I think a different interesting comparable is Uber. Both have really promising revenue growth stories, but (unlike Netflix) have no control over content/supply costs. For both Spotify and Uber ~80% of that gross revenue number goes straight to either record companies or driver commissions and rider subsidies. And the 80% does not diminish with scale.

Uber's 2017 gross revenue was 37B to Spotify's 4B, but the valuations are 50B to 30B. Think Spotify's valuation is a little overheated?