In a rite of late summer as predictable as the start of football season, Apple's (AAPL)  announcement of new iPhones typically triggers a round of promotions from AT&T (T) , Sprint (S) , T-Mobile USA (TMUS) and Verizon (VZ) . The offers for the iPhone 8, iPhone 8 Plus and iPhone X have already started, following Apple's event on Tuesday unveiling the new devices.

"The first two quarters after Apple releases a new iPhone model, Apple sees a massive sales peak," IHS Markit analyst Ian Fogg said of the carriers' annual competition for wireless subscribers. "It's doubly important for the U.S. carriers to be competitive as consumers upgrade their old iPhone with one of the latest models."

Sprint CEO Marcelo Claure tweeted an offer of half off the monthly lease for the iPhone 8 if subscribers trade in an iPhone 7.

2/7 @Sprint customers will save a TON of $$ - 50% off the monthly lease of the #iPhone 8 when you trade in your 7. Details tomorrow. pic.twitter.com/NvkA1TvLWR

— MarceloClaure (@marceloclaure) September 12, 2017

Verizon is offering $300 off an iPhone 8 or iPhone 8 Plus when consumers trade in a qualifying phone (which phones qualify is unknown so far) and sign up for unlimited service. The carrier's payments start at $29.17 per month for a two-year lease on the iPhone 8, when customers pay the full $699.99 retail price, and $33.33 per month for the $799.99 iPhone 8 Plus.

T-Mobile provides a $300 discount for customers who trade in an iPhone 6 or a newer model, although it will apply the rebate to the iPhone X as well as the iPhone 8 and 8 Plus.

The #iPhoneX looks EPIC. & you know @TMobile will carry it! Plus we're giving you up to $300 off ANY new iPhone w/ trade-in!! pic.twitter.com/EADSP3WU7A

— John Legere (@JohnLegere) September 12, 2017

AT&T has taken a different approach, offering a 32GB iPad for $99.99 when customers sign a two-year contract for the iPhone 8 or 8 Plus. The carrier also highlights that it has recently packaged HBO for free in its unlimited plans, though customers would not need an iPhone to benefit from the promotion.

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