Sonic Electronix via eBay offers the Fostex TH-500RP Premium RP Stereo Over-Ear Headphones for $329. Coupon code "CMADNESS20" cuts that to $309. With free shipping, that's tied with our expired mention from yesterday as the lowest total price we've seen. (It's the best deal we could find today by $190.) These well-reviewed open-back circumaural headphones feature planar magnetic copper foil diaphragms, aluminum cups, leather earpads, gold-plated plug, and a 20Hz to 30kHz frequency response.

Note: The coupon can only be used once per PayPal account.