Walmart offers the Plantronics DA60 USB-to-Headset Adapter, model no. 63725-01, for $78.58 with free shipping. That's the lowest total price we could find by $3. It features PerSono Pro 2.0 software and inline volume and mute controls.
Adorama offers the Plantronics Audio 400 DSP USB Computer Headset, model no. 76921-11, for $36.99 with free shipping. That's the lowest total price we could find by $2. It features a built-in USB cable, frequency response of 20Hz to 20kHz, and noise-cancelling microphone.