You'll get the promo if you've already pre-ordered (and qualify), and Sprint is quick to add that it's available to any existing customer who owns a phone on the trade-in list. You'll still get 50 percent off the lease price with a handful of other devices, including older hardware like the iPhone 6, Galaxy S7, G5 or Moto Z Droid.

It's not surprising that Sprint would up the ante for the iPhone 8 launch. The carrier reported its first profit in 3 years during its spring quarter -- it no doubt wants to keep that momentum going by adding as many subscribers as it can. As expensive as it may be for Sprint to eat the costs of your hardware upgrade, it'll likely see that as worthwhile if it lures you away from a rival such as T-Mobile or Verizon.