Audio-Technica ATH-R70x for $283 [MD]

Another offer is now unlocked at Massdrop, the new condition open-back over-ear Audio-Technica ATH-R70x in their black color scheme are going for $275 plus $8~ flat shipping. They come with a 1-year warranty from Massdrop (not Audio Technica). They will ship in mid-December 2016, and the offer is running for the next eight days. Note that these are high impedance headphones, so make sure they fit your arsenal power-wise.

Amazon is not price-matching these, but some marketplace sellers at Amazon are bundling these with a variety of DACs/Amps and other accessories for $350. The DACs/Amps bundled with them are not necessarily ideal for these headphones, but if you have various headphones and music sources, then you can easily add the extra accessories to your rotation.