GameFly discounts a selection of used video games, Blu-rays, and DVDs during its Year-End Sale, with prices starting from $3.99. Plus, all orders receive free shipping. Deal ends January 3. A couple of best bets, with comparisons to new units:
Used Call of Duty: WWII for Xbox One for $14.99 (low by $25)
used God of War for PS4 for $14.99 (low by $10)
These retailers offer some of the most consumer-friendly price-match policies anywhere.