Newegg offers the LaView 16-Channel 4-Megapixel IP Security System with Four Cameras, model no. LV-KNZNE526164N4, for $599.99. Apply coupon code "MPGAMER16" and pay via Masterpass to drop it to $574.99. With free shipping, that's $625 off list and the lowest total price we could find. It features 4-megapixel bullet cameras with resolutions up to 2560x1440, night vision, remote viewing, motion detection, and Gigabit Ethernet. Coupon ends October 31 and is limited to one use per account.
Of note, it's also available bundled with a WD Purple 4TB Surveillance Serial ATA 6Gb/s 3.5" Hard Disk Drive, model no. WD40PURX, for $676.98 with free shipping. That's an additional savings of $141 against what other stores charge for this hard drive.