Since they're based on mileage, the taxes/fees are factors.
Mexico is higher than some other countries due to the Tourism Tax and Departure Fee ($40-50) plus the usual.
Peru isn't cheap, either.
Some countries charge sep tax at the airport on exit--like Guatemala, Costa Rica Used to (haven't been for a while) and you need cash (now sometimes CC)
EZE and SCL have new $140 arrival fee (from States) of $140 (CC accepted) but sample fare is $500 ATL/SCL RT + that pesky fee, which is good for 10 yrs or life of passport.
HKG is cheap but has the mileage--same for NRT .
FRA was beastly @ $130 and ATH was $65 last week.
BCN is cheap @ $35--heading there next Monday. Loads are wide OPEN!!!
Those Asian fares under $1000 are west coast gateways, aren't they Tony?? (Of course, coach, too)