Prices of Birthright ticket extensions are determined by the specific airline that you are flying with and by Taglit Birthright Israel. Gil Travel does not determine prices and has no ability to change them.
Each airline has a base cost that you can find here, and if there are no seats available at the base class ticket (which occasionally does happen during peak travel times), the airline may offer a higher cost seat. We will NOT book you on that seat before notifying you via email and getting your approval.
You will never be charged if you do not receive a fare that you approved.