JohnK didn't point out averages, he made some anecdotal claims about the price comparison that don't match my experience. e.g. limited availability of Virgin sale fares. But in the past it has seemed that he doesn't really check for Virgin sale fares consistently. I'm also surprised because I frequently see the Virgin sale fares on the most popular ADL-SYD flight on Monday morning when the Qantas sale fare is not available on the same flight and they are asking 150% of the base non-sale fare. Basically, saying that I checked for a flight and Virgin was more expensive so I booked Qantas, is not a proper comparison for the big picture.
Without going into the variables (because I can see a range of points) it all comes out that our travel needs are so varied that it is impossible for any one of us to determine which airline is cheaper on the whole. You clearly have much more variety in your travel and I would guess you book closer to the travel date, maybe at shortish notice. What you see and what I see can't be compared. But JohnK and I have a similar travel profile, so it would be really interesting (from an academic POV) to compare what we each achieve week in, week out.