While Sprint is launching the iPhone 8 and iPhone 8 Plus on
September 22 (just like all other major US carriers), if you want to buy the
new handsets from Boost Mobile or Virgin Mobile – Sprint’s two prepaid brands –
you’ll have to wait an extra week to get them.

Both Boost and Virgin Mobile will release the two new
iPhones on September 29, likely for the same prices that Apple is asking
(iPhone 8 starting at $699, and iPhone 8 Plus starting at $799).

Boost Mobile
is already accepting pre-registrations for the iPhone 8 and iPhone 8 Plus. For
a limited time, if you pre-register, … – Source