AC is following the competition in terms of YQ charges. They are very competitive with Euro carriers ex Canada on flights to the continent. They seem to be very close to BA on routes between Canada and LHR. The YQ charge seems to fluctuate somewhat depending on the season so I presume it follows a pattern as a % of full fare tickets which is what BA does as I am told.

Thus charges to Asia are quite a bit less as they are keeping up with the competition on direct overseas flights ex Canada.