BuyDig offers the Audio-Technica QuietPoint Active Noise-Cancelling Headphones, model no. ATH-ANC27, for $44.95 with free shipping. That's the lowest total price we could find by $15, outside of the deal below. (We also saw them for $5 less last spring.) They feature 40mm drivers and up to 18dB of noise reduction. Deal ends February 14.
A close price: PricePlunge offers the virtually identical ATH-ANC27x model for $47.49 plus $2 for shipping via code "coldplunge5".
Update: Specs corrected