MP4 Nation via Amazon offers Prime members the Brainwavz Beta Noise-Isolating In-Ear Headphones, model no. BETA, for $12 with free shipping. (Non-members can spend $25 or more to get free shipping; otherwise it adds $5.07.) That's the lowest total price we've seen for any Brainwavz headphones. Sales tax is added where applicable. They feature 20Hz to 20kHz frequency response, 13.5mm drivers, and more.

Also available is the Brainwavz R1 In-Ear Headphones with Microphone for $25 with free shipping, another price low. They feature an in-line microphone and remote, 20Hz to 22kHz frequency response, and more.