I recently bought 2 Economy W fares to be able to use my GPU's. Here are the fare/taxes breakdowns:

LAX-GIG-LAX (W fare)

1 Adults (age 18 to 64) $1,808.00
Taxes/Fees

U.S. Customs User Fee $5.50
U.S. APHIS User Fee $5.00
U.S. Federal Transportation Tax $33.40
U.S. Immigration User Fee $7.00
U.S. Passenger Facility Charge $10.50
September 11th Security Fee $7.50
Brazil Embarkation Tax $36.00
TOTAL $1912.90

LAX-SYD-LAX

1 Adults (age 18 to 64) $1,593.00
Taxes/Fees

U.S. Customs User Fee $5.50
U.S. APHIS User Fee $5.00
U.S. Federal Transportation Tax $33.40
U.S. Immigration User Fee $7.00
Australia Passenger Service Charge $51.00
Australia Passenger Movement Charge $47.00
International Surcharge $680.00
U.S. Passenger Facility Charge $4.50
September 11th Security Fee $2.50

TOTAL $2428.90

I called UA and asked what the $680 international surcharge was for the SYD flight - they said it's a fuel surcharge.

Both the Rio and Sydney flights are about a 14 hour flight (roughly). Why does the SYD flight have a $680 fuel charge and the Rio flight $0.

Both flights are on all UA metal.