V&M Innovations via eBay offers the refurbished Sennheiser HD428 DJ Stereo Headphones for $29.99. With free shipping, that's $19 under the lowest total price we could find for a new pair, although we saw a refurb pair for $6 less in August. They feature a 18Hz to 22kHz frequency response, noise-isolation earcups, 3.5mm plug, 1/4" adapter, and more.

Note that a 90-day V&M Innovations warranty applies.