Sounds like the pricing structure all works together very well, then. 5 hours per day sounds like a good point which plenty of people can easily eclipse, but the majority will not, keeping the service profitable.
Yes, but they said it was 50% of revenues. I believe Pandora is profitable, so the sum of all other costs must be less. This means that the breakeven point is actually somewhere between 2.5-5 hours. 5 hours per day is not a magic number- I think 4 or 3 also sound perfectly fine, based on the usage patterns I see.