Yes, as an iTunes customer you are paying for the right to be sold as part of the iTunes platform. More customers means a more valuable platform enabling Apple

Yes, as an iTunes customer you are paying for the right to be sold as part of the iTunes platform. More customers means a more valuable platform enabling Apple to cut more lucrative deals with its partners. They are right to brag about the number of credit cards on file. It's similar to AT&T really. AT&T does not set monthly fees by dividing up the cost of running its network among all subscribers. Instead it sets competitive fees which will allow it to grow a big customer base. Then it tries to extract revenue from those customers by any means: normal fees, overage charges, selling apps or content, partnerships, advertising, whatever it can think of. Media companies try to make money as a company, not on each transaction. An alternative strictly-fee-for-service approach would have to charge a lot more, and would likely not get enough customers to stay afloat.