Newegg via eBay offers the refurbished Vizio 50" 4K 120Hz LED LCD Ultra HD Smart Television, model no. P502ui-B1E, for $367.41 plus $49.99 for shipping. That's $83 under our January refurb mention and the lowest total price we've seen. (It's the best today by $33.) It features a 3840x2160 native resolution, 120Hz refresh rate, 2-sided remote with QWERTY keyboard, USB, and five HDMI inputs.
Note: A 90-day warranty is provided, but it is unclear who backs it.