An ebay deal is letting you have the Galaxy S8+ G955FD Dual SIM version for a cent under $630 in the US. This one comes packing Samsung’s own Exynos 8895 chipset as opposed to the Snapdragon 835 that's normally available in the country.
Keep in mind that the Dual SIM device features a hybrid slot, so you'd have to live without microSD memory expansion option if you take advantage of that and rely on the 64GB of built-in storage only.The Galaxy S8+ for $629.99
The seller ships to a number of countries around the world, but getting the device outside the US will incur import fees, which will probably negate all of the savings.
At time of writing Maple Gold, Coral Blue, Midnight Black and Orchid Gray were still available, so you’re out of luck if you wanted Arctic Silver or Rose Pink.