Cheapest I have found online, with free delivery to metro area in Australia.
JB HIFI selling for $269
Sennheiser site selling for $329.95
Seems like a steal for a high rated noise cancelling headphone.
The HD 4.50 BTNC Wireless Bluetooth Headphones with NoiseGard Active Noise Cancellation from Sennheiser feature high-quality sound and Bluetooth 4.0 technology in a sleek and foldable design. These headphones can be used to listen to music and answer calls, and are well suited for use with smartphones, MP3 players, tablets, and other portable devices.
Spend an extra $15 and you can use the $10 newsletter coupon