Edited December 23, 2017
at 09:43 AM
Amazon has the Sennheiser HD 599 Open Back Headphone [amazon.com]
for $135.69 with free shipping.
Seems to be the lowest price ever on the headphones thus far by $64, normally $199.99 since October 2017, MSRP $250.
Note: Price has gone up to $136.90