Newegg's eBay shop has the Acer XG270HU 27" monitor on sale for $329. It is the cheapest price I have seen for a 27" 144Hz 1440p monitor. It is a TN panel, but for the price it seems to be a great deal. I have included more information from Newegg's website about the panel below and a link to the product. Enjoy!
"Take your gaming and movies to the next level with the Acer XG270HU monitor. It features 27" large viewing real estate and 2560 x 1440 WQHD resolution that delivers every bit of detail. Everything looks fantastic on the screen thanks to the fast 1ms response time, 144Hz frame rate and ACM 100,000,000:1 contrast ratio. It also supports FreeSync technology, for tear-free and stutter-free gaming. HDMI, DVI and DisplayPort inputs are built onboard. Plus, its frame-less design with arresting red stand are easy on the eye, while the flicker-less, low dimming and Comfy View technology ensure the Acer XG270HU are comfortable to your eyes."
"The high resolution of this monitor (WQHD, 2560 x 1440 pixels) combines with a rapid refresh rate of 144Hz and a blazingly fast response time of 1ms to deliver ultra-smooth action sequences in great detail. This is also the world's first frameless gaming monitor, so all that action is free to go where your mind goes."
"As a high-end gaming monitor, the XG is designed to handle high rates of data transfer. To get all that data to the monitor quickly and smoothly requires high-bandwidth data cables. That's why these monitors come with high-bandwidth connection ports like HDMI 2.0, DVI (Dual Link), and DisplayPort."