Walmart offers the refurbished Vizio SmartCast 55" 4K 2160p LED-Backlit LCD Ultra HD Smart Display, model no. E55-E2, for $379.99. Choose in-store pickup to drop it to $371.25. That's $159 under the best deal we could find for a new one and the lowest price we've seen for this display in any condition. (It's also $29 below our December mention of a new unit.) It features a native resolution of 3840x2160 (4k, 2160p), Chromecast with Smart TV apps, octa-core processor, 802.11ac WiFi, USB, Bluetooth 4.1, and four HDMI inputs.
Note: No warranty information is available, although the seller does offer a 90-day return policy.