Actually, the digital distribution partners that Sony license to sell their music on their behalf will be the ones paying for the bandwidth. As far as the label is concerned, the profit they make is essentially the same margin they would expect from a retail sale, in that they have already forked out to get the content onto the shelves/servers. Much in the same way that a record shop would pay the label for the copies of the album, pay for the consignment to be delivered and then pay their staff to stock it on the shelves.
So yes, Sony have probably done rather well out of this.
Ask five economists and you'll get five different explanations (six if one went to Harvard). -- Edgar R. Fiedler