Rated De,
I would suggest that Qantas have a few extra aircraft than JQ but a much greater seating capacity to earn a higher revenue. (Would be interesting to know the total seats of both - think Q have some freighters on the books??)
JQ by all reports has lower staff costs and a much newer (fuel efficient) fleet. These two factors being biggest costs to companies.
So in some cases it is good to only get 25% of revenue - just depends how much marble you like in your cut of beef.
That said I doubt very many JQ flights into Canberra, but lots of revenue for Qantas.