To estimate day-to-day average prices, KAYAK will take all prices for every day ahead of departure over the past yr for first class flights to Sydney, removes the best 0.1% to account for outliers, after which you can can take the common of all of the values for each month. https://livebookmarking.com/story18577153/examine-this-report-on-first-class-plane-ticket-to-copyright