Sonic Electronix offers the Sennheiser HD 419 Over-Ear Headphones for $19.99 with free shipping. That's $8 under our mention from last month and the lowest total price we've seen. (It's a current low by $12.) They feature neodymium magnet drivers, a 20Hz to 20kHz frequency response, 108dB sensitivity, and 4-foot cable.
Of note, you can buy two for $33.98 with free shipping. (Scroll down and click "Add Both to Cart" to get this price.) That's $17 per set and by the far the best price we've seen.