Missus VH and I have been doing a lot of inter state trips recently out of our own money so have been careful about getting good deals. Time and time again, QF has been cheapest or equal cheapest when comparing similar flight times and taking a checked-in bag. And that's ignoring the possible additional expense for an in-flight snack which is free on Qantas.
Not sure what load factors the others are getting but all the flights we've been on have been relatively (est. 90%+) full.
Oh, had to book daughter onto a Jetstar recently due lack of availability of any other options. They made her take 2kg from her cabin bag and put it in her checked baggage. Seriously, how does that help?