Sprint currently has 3 pre-paid brands: Boost Mobile, Assurance Wireless and Virgin Mobile. It's adding another that will sell pay-per-minute services. (Name to be determined).

Boost Mobile is a flat-rate all-you-can-eat plan at $50! Less than the post-paid plan at $70 + taxes and fees.

Per Engadget: "Sprint Nextel, through its Virgin Mobile brand, has announced a pretty big shift in its business model by offering new prepaid plans that begin at a mind-blowing $25 a month. Starting on May 12, three new Beyond Talk plans will include unlimited messaging, email, data, and web, as well as 300 minutes ($25), 1,200 minutes ($40), or unlimited minutes ($60) of talk time. And that ain't all -- BlackBerry data service can be added for an additional $10. Of course, you'll be paying full price for your phone, but at least the selection is indeed better than the usual pre-paid fare, including the Blackberry Curve 8530 ($300) and LG Rumor Touch ($150). We don't know how the other carriers are going to respond, but this does prompt the question: would you put up with Sprint's handset selection for a plan this cheap?"

It seems like Sprint is going all in with pre-paid and the reult will be lower ARPU and uncertain ARPU. MetroPCS probably has the most to lose here, which makes a merger here seem apparent.