That's a fascinating way of looking at it that I've never thought about before. So basically Spotify is considering cost per minute of music vs. podcasts? That's a believable explanation for the counterintuitively high price they paid for acquiring popular podcasts like Joe Rogan (which they know loyal viewers users will reliably watch for hours each week, during which time they won't be streaming Taylor Swift songs on repeat).

It's also interesting because the normal optimizations like caching don't apply to licensing fees. At first I was going to suggest that they can cache frequently played songs to save cost, but then I realized that has no impact on royalty fees derived from playtime.