Best Buy offers the Sony In-Ear Stereo Headphones in Violet, model no. MDRE9LP/VLT, for $6.99. With free shipping, that's the lowest total price we could find by $4 (outside of the mention below). Sales tax is added where applicable. These earbuds feature 13.5mm drivers and a 18Hz to 22kHz frequency response.

A close price: Electronics Expo via Amazon has them for $3.44 plus $2.99 for shipping, however stock is very limited.