CowBoom offers the used 4th-generation Apple iPad 16GB WiFi Tablet with Retina Display in Black, model no. MD510LL/A, for $164.99 with free shipping. That's $55 below our August mention of a refurb and the lowest total price we've seen for this model in any condition. (It's also $68 under the best price we could find for a refurb today and $180 less than the best deal for a new unit.)
Note: No warranty info is provided.