Then again, Sprint just bought VMUSA for its customers.
Actually Sprint bought Virgin Mobile to strengthen their prepaid position as they feel that's where their growth will come from. Virgin customers were already being counted among Sprint's numbers anyway since they utilize Sprint's CDMA network.
Getting the MVNO out of the picture except for brand licensing makes those subscribers more profitable. Sprint has been MVNOing itself like a whore for many years, since they can't get customers themselves and are desperate for them. The MVNO customers break even to Sprint I think. Most MVNOs are Sprint, in the USA, for a reason.