For completeness/interest, realized that aa.com does break out the taxes/fees, and for the LHR-BLR routing on BA, the breakdown is roughly 2/5 taxes, 3/5 BA surcharge:
CARRIER-IMPOSED FEES $543.20 USD
PASSENGER SERVICE CHARGE $3.65 USD
INDIA
DEVELOPMENT FEE $11.20 USD
INDIA
USER DEVELOPMENT FEE $25.08 USD
INDIA
PASSENGER SERVICE CHARGE $75.60 USD
UNITED KINGDOM
Air Passenger Duty (APD) $289.50 USD
UNITED KINGDOM
Total Adult taxes and carrier-imposed fees $948.23 USD Per person