Newegg offers the Asus 28" 4K Ultra HD LED-Backlit LCD Monitor in Black, model no. MG28UQ, for $409.99 plus 99 cents for shipping. That's $190 off and tied with our expired mention from six days ago as the lowest total price we could find. It features a 3840x2160 native resolution, LED backlight, built-in speakers, and HDMI and DisplayPort inputs.
Note that Amazon charges $409.99 with free shipping, however stock is limited.