Costco – Samsung Galaxy S9 (T-Mobile) for $319.99 or S9+ for $439.99 after trade in credit of $360

Looks like Costco has the lowest prices on the Samsung Galaxy S9 (T-Mobile only). S9 is $679.99 and S9+ is $799.99 if you buy outright. With $360 trade in credit, the price of the S9 is $319.99 and the S9+ is $439.99.
http://membershipwireless.com/content/offer8
Pricing only applies to outright purchases, if you finance the phone the retail price is higher
$360 trade in devices:
Galaxy S8 / S8+ / S7 / S7 Edge / Note8
Apple iPhone 8 / 7 / 6s
$200 trade in devices:
Galaxy S6 / S6 Edge / S6 Edge+ / S5 / S4 / Note5 / Note4
Apple iPhone 6 / 6 Plus / 5s / SE