eBay with buydig has the Microsoft Surface Duo 256GB 8.1" (Combined) PixelSense Fusion Dual-Screen Folding Android 10 Smartphone/Tablet, AT&T LTE Unlocked, 2020 model (Glacier, TGM-00001) for $400 - 20% off with coupon code COUNTDOWN22 [Exp 10/23] = $320 with free shipping. 

Two PixelSense Fusion 5.6” (1800x1350, folded) touchscreens open up to 8.1”.

• Qualcomm Snapdragon 855 Octa-Core, 6GB RAM, 256GB storage
• 8.1" AMOLED (1800x2700 combined), 11MP rear camera, 4K video@30/60fps
• 802.11ac, Bluetooth 5.0, fingerprint sensor, USB-C, Android 10