The unlocked Galaxy Note 9 is cheaper at Microsoft and Best Buy than at Samsung
To be clear, $799.99 is what Microsoft and Best Buy are asking for the Galaxy Note 9 128 GB. The Note 9 512 GB is offered for $1,049.99 - that's $200 off what Samsung is currently asking ($1,249.99). Additional savings - up to another $100 off - are available at Best Buy if you want to activate your Galaxy Note 9 on Sprint, Verizon, or AT&T.
There are no differences between the unlocked Galaxy Note 9 handsets found at Best Buy and Microsoft and those sold directly by Samsung. Thus, US warranty and compatibility with all relevant carriers are guaranteed.
Since the Samsung Galaxy Note 9 is now a bit over 1 year old and it's been eclipsed by new Galaxy Note 10+, its price has been discounted many other times before. However, at this very moment, you won't find better deals than those presented above - at least not when we talk about unlocked Note 9 units that are brand new and come with US warranty.