[PHXFlyer]

I took the liberty of duplicating your exact itinerary on AC.com. Here's the breakdown of the fare, taxes, surcharges and fees for a paid business class ticket from Winnipeg to London Heathrow on the same dates and flights in CAD:

Fare Summary Passenger Type Adult Base Fare (C7M0GB,Z14M0GB,C0EXB) 8231.01 Surcharges NAV 17.99 Fuel Surcharge YQ 380.00 Taxes, Fees and Charges Canada Airport Improvement Fee SQ 28.00 Air Travellers Security Charge (ATSC) CA 17.00 U.K. Passenger Service Charge UB 34.63 Canada Goods and Services Tax (GST/HST #10009-2287) XG 1.40 U.K. Air Passenger Duty GB 140.65 Total airfare and taxes before options (per passenger) 8850.68 Number Of Passengers 1 Grand Total - Canadian dollars $8850.68 CAD

So, if you add up all of the taxes, surcharges and fees, it totals $619.67 CAD. You are not being asked to pay any more in taxes and fees than any other person purchasing a business class ticket to London with the exception that you are "purchasing" your base fare with miles instead of money.