CowBoom offers the used Sony PlayStation Vita WiFi System, model no. PCH-1001, for $119.99. Coupon code "Vita20" cuts it to $99.99. With free shipping, that's tied with our December mention as the lowest total price we've seen for this model. (It's also $84 less than another used unit and $115 below the best price we could find for a new one.) It features a 960x544 multi-touch 5" OLED, multi-touch pad on the rear of the device, dual analog sticks, and front- and rear-facing digital cameras.
Note: No warranty information is provided. Also, this used unit is a grade 4 and may be missing parts or accessories and have significant scratches or scuffs.
Walmart offers the Sony PlayStation 4 500GB Gaming Console, model no. 10034PS, for $399.99 with free shipping. (Amazon offers it for the same price.) Outside of bundles, that's the lowest total price we could find by $120. It includes the system, a DUALSHOCK 4 wireless controller, wired headset, and cables.
Update: It's now out of stock at Walmart; however, Amazon still offers it for $399.99 with free shipping.