As long as (Long-Term Increased iTunes Store Revenue due to Ping) > (Development and Maintenance Costs of Ping), I can't see why it's surprising. Perhaps you disagree that the above equation will be true for Apple?
Personally, I think the offline play feature makes it worth it. None of the other on-demand services seem to charge any less for mobile either, which makes me think that the labels have put a price floor on mobile access.
Oh I did forget about that... although I wish it had some sort of auto playlist feature that mixes in recommended music... basically I want it to be Pandora that lets me sometimes choose songs.
