For in-store pickup only, and with stock varying by ZIP code, Costco offers a $175 Costco Gift Card and a $25 Costco Gift Card for free when you purchase an Apple iPhone 7 or 7 Plus for T-Mobile on an upgrade or a new line of service via an installment billing plan. (Scroll down to see the offer.) Assuming you'll use the gift card, that about $200 less than you could expect to pay direct from T-Mobile. Deal ends March 31.
Looking for other carriers? We saw a similar deal with a $300 Target Gift Card for Verizon, AT&T, or Sprint yesterday.