Deal: Unlocked Samsung Galaxy Note 9 drops to just $650 on eBay10
Of course, there are some downsides like the fact that it usually doesn't include support for CDMA carriers such as Sprint and Verizon. Also, most of the time these unlocked Galaxy Note 9 phones don't come with U.S. warranty.
In any case, if none of the above bothers you, eBay seller never-msrp has the Samsung Galaxy Note 9 on sale for just $650. The phone comes unlocked and features dual-SIM support, but, as mentioned earlier, it will only work on GSM carriers (AT&T, T-Mobile).
Furthermore, since this is the international version of the Galaxy Note 9, it will pack Samsung's Exynos 9810 processor instead of the Qualcomm Snapdragon 845 that comes inside the U.S. model.
At the time of writing, only the Ocean Blue and Midnight Black colors are still up for grabs on eBay (Metallic Copper, Lavander Purple are out of stock).