Sonic Electronix via eBay offers the Philips ActionFit In-Ear Headphones in Pink/Gray, model no. SHQ1200, for $10.37 with free shipping. That's the lowest total price we could find by $8, outside the mention below. They feature neodymium drivers, Kevlar reinforced cable, and a frequency response range of 20Hz 30Hz to 20kHz.

A close price: BigDeals via eBay offers has an open-box unit in Orange/Grey for pennies more. These are considered new and unused, although they may be missing the original packaging.

Update: Specs corrected