Payments: Visa, Paypal, Amex, MasterCard, and many others would gladly handle the payments for ~2%. Not sure where you're getting anything about inventory and shipping given it's digital content. Sales: when did actually do any selling for anyone's product other than when it was mutually beneficial? You still need to sell it to people to actually use your product. Publishing: again, what is apple doing here? Distribution and a little bit of marketing, sure - but that's certainly not worth the other 28% of revenues.
Also don't see why Rhapsody repackaging stuff makes it any different. Shouldn't a true app store model work for any type of business?