While the unlocked Lumia 950 XL is $649 and perpetually out of stock at the Microsoft Store, Expansys USA is offering a much better deal. They are selling the handset for only $564.99 unlocked , 19% down on their usual asking price.
The handset has LTE hands for both T-Mobile and AT&T, and also metroPCS, Cricket and other smaller GSM carriers.
Expansys notes that they do not have the handsets in their warehouse, suggesting some inquiries may be in order to make sure the delivery times are acceptable.
See the deal at Expansys here.