Originally Posted by
stargold
Something of a stab in the dark, but I believe YQ can sometimes depend on the "place of issue" - that is, a revenue ticket ex-HKG will be "issued" in HKG using the HK government-regulated (and lower) YQ ex-HKG, but the Avios ticket could be "issued" in London which may trigger the LHR-based longhaul YQ which is higher.
This appears to be exactly it. Approx figures below:-
Ticketed in Hong Kong
BA YQ surcharge (YQ) HK$1,353.00
United Kingdom Air Passengers Duty (GB) HK$323.00
United Kingdom Passenger Service Charge (UB) HK$99.00
United Kingdom Passenger Service Charge (UB) HK$87.00
Hong Kong Departure Tax (HK) HK$120.00
Ticketed in London
BA YQ surcharge (YQ) £213.00
United Kingdom Air Passengers Duty (GB) £26.00
United Kingdom Passenger Service Charge (UB) £7.90
United Kingdom Passenger Service Charge (UB) £6.94
Hong Kong Departure Tax (HK) £9.70
£213 equates to about HKD 2635, so an increase in YQ of HKD 1282 or £103.63 for ticketing in the UK.
ISTR that YQ is capped by regulation for tickets issued in Hong Kong.