Last-generation phones are expected to depreciate, but Samsung phones typically retain their value better than many of their competitors. It's pretty surprising, then, that Samsung is currently offering the T-Mobile Galaxy S8 for only $350, around $400 off the launch price and $250 off the current MSRP. If you don't mind not having the latest and greatest thing and you're on Team Magenta, you may want to look into this.
US models of the Galaxy S8 come with a 5.8" 1440p AMOLED display, a Snapdragon 835, 4GB of RAM, 64GB of storage, a 12MP camera, an 8MP front-facing camera, and a 3,000mAh battery. IP68 water resistance, an iris scanner, fast wireless charging, and MST for Samsung Pay are present as well. Even today, it's still a pretty well-equipped phone.
Samsung is only discounting the T-Mobile S8 in Arctic Silver to $350. No contracts or trade-ins are needed; just pay and you'll receive your phone in the mail in a couple of days. Financing is available (but not mandatory for this), and shipping is free. It's worth noting that this can be used to get an effective $150 discount on the Note9 if you're planning to pick one of those up, as this has a trade-in value of $500 with T-Mobile. Hit the source link below to pick one up; we wouldn't be surprised to see this sold out soon.