I believe this is the cheapest I have ever seen them. These are one of the most stylish and best sounding portable headphones out there, and have been for years. These are not the wireless ones, so they do not have Noise-Cancellation. But they are closed headphones, so if you have music playing, it's very hard to hear others around you or for them to hear what you're listening to (isolation is great on these from my personal testing). They do sound better than the wireless ones in my opinion (sound stage is not as narrow as the wireless, bass is more punchy and detailed, and mids are clearer).
Up until a few weeks ago JBHiFi had them for $449, but they are currently $284 at JBHiFi, and a few months back they had them for $299. So their price has been going up and down over the last few months, but as I mentioned at the start of the description, I believe this is the lowest price I have seen them in Australia, with free delivery as well.
Personally I run these with a Fiio Q1 Mark II DAC/AMP which I purchased from AddictedToAudio, and I use the NewFantasia Replacement Audio Upgrade Cable for Sennheiser Momentum, which is available on Amazon AU too.
Great price! Got them from ATA some time ago for use when travelling (they're super portable, comfortable on long hauls, good isolation and have an enjoyable sound, even if not entirely accurate). Highly recommend at this price.