You can (allegedly) buy a Nexus 6P from the Google Store. Heck, that's basically the only place that comes to mind. But if you don't think you can get the phone elsewhere, you're wrong. Huawei will also sell you the phone directly from its site.
Yes, altogether we're talking about spending a pre-tax minimum of $850 and reducing that down to just $800, but money saved is money saved. Both of these are premium Android devices at the top of their class, so you already know they're going to cost you. Now they're just going to cost you $50 less.