CowBoom offers the used Microsoft Xbox 360 4GB Slim Console, model no. RKB-00001, for $59.99 with free shipping. That's $50 under the lowest total price we could find for any new or refurbished Xbox 360 console, although we saw a used unit for $5 less in August.
Note: No warranty information is available. This used unit may be missing parts or accessories and have dents, scratches, or other cosmetic blemishes.