To compute everyday regular prices, KAYAK will take all prices for on a daily basis right before departure during the last yr for first class flights to Sydney, removes the top 0.one% to account for outliers, after which you can can take the average of all the values for monthly. https://businessflightshop.co.uk/blog/what-should-you-know-before-booking-a-business-class-flight-to-south-africa-ticket-from-uk/