Best Buy via eBay offers its Dell S2719DM 27" 1440p HDR Flat IPS LED-Backlit LCD Ultrathin Monitor for $269.99 with free shipping. That's $63 under our May mention and the lowest price we've seen. (It's the best deal today by $75.) It's 5.5mm at its thinnest and features a 2560x1440 native resolution and two HDMI inputs.
June brings some big deals and sales, but you're better off postponing certain purchases.