Newegg offers the Changhong 42" 4K 2160p LED-Backlit LCD HDTV, model no. UD42YC5500UA, for $399.99 with free shipping. That's $500 off and a very low price for a 42" 4K television. It features a 3840x2160 native resolution (four times that of 1080p TVs), LED backlight, USB port, and four HDMI inputs.
Of note, Newegg has it with a wall mount for just a buck more.