VM Innovations offers the refurbished Sennheiser HD428 DJ Stereo Headphones for $39.95. Coupon code "16OFFHD" drops it to $23.95. With free shipping, that's $56 under the lowest total price we could find for a new unit, although we saw a refurb for a buck less in April. They feature a 18Hz to 22kHz frequency response, noise-isolation earcups, 3.5mm plug, 1/4" adapter, and more.

Note: A 90-day warranty applies, although it's unclear who backs it.

Update: Coupon code corrected.