Mid week (Tues/Wed/Thurs) departure fares in both directions are cheaper than departure on other days - by several thousand dollars.

I just came from Australia in April. Booked it last fall. It was about $6200 (all inclusive) return on AC for April if flying on one of those 3 days in both directions - much more expensive on other days of the week by several thousand dollars.

But I do not know your definition of "winter" flying. That is summer in Australia and winter in Canada -so I would expect prices to be much higher than in spring, fall, or even summer seasons (in Canada).