Best Buy has a deal on the Samsung Galaxy S9, Galaxy S9+ and Galaxy Note 8 as long as you are willing to purchase and activate your new phone on Verizon, AT&T, or Sprint with a monthly installment plan. Unlocked models are unfortunately not part of this deal.
The $300 savings will not be instant. Instead you will see it reflected as reduced monthly payments over the life of the device. After 24 months (or 30 months on AT&T Next), you will end up paying around $650 for a Galaxy Note 8, around $490 for a Galaxy S9, and around $600 for a Galaxy S9+.
The deal doesn't require a new line of service, but will require you to stay with Verizon, AT&T, or Sprint for up to 30 months. If this is a deal you will be interested in, follow the source links below to purchase a new Samsung flagship device.
source - Best Buy