The taxes are related to which ariports and countries you fly through and differ if you are transiting as opposed to stopping over. Perhaps you are stopping in expensive places? Or lots of them?

I just ticketed through AA affiliate in CAI on an AONE4 and taxes were 2706 EGP, which is 6.6% on top of base fare.

You could look at this site and do some calcs of your own.

http://www.consolidatedtravel.com.au/qf/taxes.asp

You will need to fire up your favourite currency conversion site though. It is an Aussie web site.