Do not book with Webjet. They are a fraudulent operation. I canncelled my wifes ticket 3 weeks prior to the flight and requested the taxes portion of the ticket. Webjet refused. Airlines will refund the tax portion if a flight is not taken as the tax is not paid to goverments until the flight is taken. As a result of Webjet refusing to refund the taxes they can pocket the money as additional profit.
Fly on workdays: As many passengers prefer to fly on week-ends, week-end tickets sell first. If you don't book your trip well in advance (2-3 months beforehand) you may notice, for example, that Thursday flights are cheaper than Sunday flights. Some low cost carriers have special promotions on the flights during the week.