Note: You can get a refurbished 39/50-inch versions from Amazon Warehouse for $373/$569.
The prices of 4K TVs continue to drop with Seiki leading the way. Amazon is currently selling the 39-inch for $405.27 with free shipping. The 50-inch version is $625.37 with free shipping. Both are all time price lows for 4K TVs
While these are HDTVs, many will use them as computer displays which yield 3840×2160 resolutions. They run 4K at 30Hz via HDMI 1.4 or 1080P at 120Hz and get 4/5 star reviews. They have 3 HDMI inputs, Tuner input and 2 USB inputs and support 4K upscaling.