Dell’s P2715Q 4K monitor has always been one of the most affordable 27” 4K IPS display on the market, but today, it’s all the way down to $400, within $20 of the best price we’ve seen.
If you aren’t familiar, IPS displays boast superior color accuracy and viewing angles compared to the TN panels you’ll find in most inexpensive 4K monitors. I own the 24” model of this exact monitor, and I absolutely love it, just make sure your computer is powerful enough to drive it.