Originally Posted by jimb

My guess is that they are charging a normal sales tax on your ticket price (or price assumed for your ticket if you are using airmiles). If the sales tax is lets say 5% then the taxes would be higher on your first class ticket because your ticket's value is much higher than a coach seat's value (or assumed value if your using airmiles). The assumed value of your first class ticket might be $900 where ass your girlfriends coach ticket assumed value might be $450. You would in turn have to pay more sales tax which would increase your overall "taxes/surcharges" higher than your girlfriends coach ticket.

Jim