To calculate day-to-day regular charges, KAYAK can take all selling prices for every single day just before departure over the last year for flights from London Heathrow Airport to Austin, eliminates the highest 0.1% to account for outliers, then can take the normal of the many values for each month. https://firstclassflightstohouston.politics.blog/2024/09/08/what-should-you-know-before-booking-tickets-for-flights-to-memphis-from-uk/