Dream-Seller via eBay offers the Crossover 28" 4K 2160p LED-Backlit Ultra HD Monitor, model no. 289K, for $269.90 with free shipping. That's the lowest total price we could find by $66. (It's also tied with the best price we've seen for a 28" 4K UHD monitor.) It features a 3840x2160 (2160p) native resolution, remote control, DisplayPort, and three HDMI ports.

Of note, this item ships with a Korean Free Voltage Type-C plug, and an adapter will be required for US use.