Micro Center has an AOC AG271UG 27" IPS 4K monitor with G-Sync for $399.99. This is the same deal as the Newegg one from last week (which expired but was on FP), but this one is from Microcenter.
http://www.microcenter
The only thing that might be a negative is that it is only 60Hz, but very few high end video cards can output that at 4K while gaming in ultra settings anyways.