Get this - Best Buy is offering up to $262.50 for Nexus 4 trade-ins. This offer is valid regardless of whether you're handing over the 8GB or the 16GB model. As long as your device is in relatively good condition and you have the necessary peripherals, you're good to go. Just move quickly. Considering the Nexus 4's $100 price drop last month, this probably won't go on for long.
Unsurprisingly, how much you get depends on the condition of your device.