Costco and T-mobile is offering up to $390 for trade in

Starting 12/7/18, T-Mobile and Costco is offering up to $390 for eligible trade ins when purchasing an Apple iPhone XR/XS or XS Max.
How to get the deal:
Go to a Costco warehouse and purchase the Apple iPhone XR, XS, or XS Max at Full Retail Price on any Post paid T-mobile account. Then go T-mobile’s Rebate page and use promote code COSTCOAPPLE390 to redeem rebate.
Official T-mobile offer with more details