CowBoom offers the used Sony PlayStation Vita WiFi System, model no. PCH-1001, for $99.99 with free shipping. That's $10 under our mention of a used unit from last month and the lowest total price we've seen for this model. (It's also $84 less than another used unit and $100 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.
Amazon offers Prime members the Sony PlayStation Vita Protective Film 2-Pack for $1.98 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $4.98.) That's the lowest total price we could find by $3 . This official Sony product protects against scratches, dirt, and dust.
Update: Note that this item is temporarily out of stock, but can still be ordered at this price for delivery when available.