Similar to the previous Bose QC35 II post from Ryanhunt, Qantas currently have the Bose QC35 II Midnight Blue NC headphones at 20% off (Save 17,430 points). Works out at $392.17 delivered + 2,000 points.
Far from cheap, but the cheapest I could find online.
Bose - $499
JB Hi-Fi & Amazon - $496
AudioHUb - $433
Video Pro - $428
From all accounts, these are not as good as the Sony WH-1000XM3B, which are also on sale with Qantas as posted by kaykay4 but there might be some Bose diehards that want these. The blue isn't too shabby.
Ends 20th December or until stocks last.