eBay has the Apple iPhone 6s 16GB No-Contract 4.7" Smartphone (Space Gray, Silver, Gold or Rose Gold) refurbished for $210 with free shipping. Features 4.7-inch (diagonal) LED-backlit widescreen multi-touch display with IPS technology, new 8-megapixel iSight camera with 1.5µ pixels, A8 chip with 64-bit architecture. M8 motion coprocessor, 1080p HD video recording (30 fps or 60 fps).
eBay has the Unlocked Galaxy S8 64GB Dual-SIM Phone (Gold, Black, Gray) for $470 with free shipping. Features 8-core (2.3GHz Quad + 1.7GHz Quad) processor, 6.2" 2960x1440 touchscreen Super AMOLED LCD, 4GB RAM, dual 12MP rear cameras with 4K video recording at 30fps, 8MP front camera, Android 7.0 Nougat OS.
For Prime members only, Amazon has the Unlocked LG Q6 32GB 4G LTE Android Smartphone (Platinum, LGUS700) for $190 with free shipping. Features 5.5" 2160x1080 display, Qualcomm Snapdragon 435 1.4GHz octa-core processor, 3GB RAM, 32GB storage, dual 13-megapixel HDR cameras, Android 7.1.1 (Nougat).
Has good Amazon Reviews.
eBay has the Samsung Galaxy S9+ Dual SIM Unlocked 64GB 6.2" Smartphone ((Midnight Black or Titanium Gray)) for $700 with free shipping. Retail price: $900. Features Exynos 9810 Octa-Core CPU, 6GB RAM, 64GB storage, 6.2" AMOLED (2960 x 1440), 12MP cam, 802.11ac, Android 8.0 Oreo.