Christmas Holiday Melbourne to Cairns Flights?

please help i want to go to cairns this christmas but the flights to cairns are shocking… yes i do understand its christmas and flights are expensive but whats the cheapest option for returning flights Melbourne to cairns 25/12/14 depart 28/12/14 return DATES NOT FLEXIBLE.. i looked up a lot of travel websites and they are all over $500 per person. If anyone can find me a cheaper option that will be great.