Cowboom offers the used Sony DualShock 4 Wireless Controller for PlayStation 4 in Black, model no. 711719100379, for $24.99 plus $5.24 for shipping. That's $20 under the lowest total price we could find for a new unit in any color and the best price we've seen for a DualShock controller in any condition. (For further comparison, we saw a new unit last month for just $5 more.)
Note: No warranty info is provided.