Update on my attempt to uncover where the extra taxes are coming from on a re-route (see post 887):

* The current number being proposed is an increase in taxes of $420. At AA's suggestion the fare is being sent to the rates desk for top to bottom checking. We'll see if that helps, else me next step will be to drop the SIN-xDOH-JNB to see if that helps.

* I had a thought and checked the taxes etc. that would be charged if I booked the various flights using AA miles. E.g. QR would not change any YQ (it's $30 to fly SIN-xDOH-JNB on miles). LHR-JFK is "only" ~$200 (so I was expecting that increase).

Question: should the taxes/fuel charges on an award ticket issued by AA match the taxes/fuel charges on an xONEx ticket issued by AA (for an identical itinerary and airlines flown of course)?