When booking flights with Avianca directly,
and when arriving via Google Flights,
clicking the Purchase conditions link followed by the Full Rule Text brings up this condition:
SR.SALES RESTRICT BETWEEN LIM AND JUL FOR SZY07TNQ TYPE FARES
TICKETS MAY ONLY BE SOLD IN PERU.
NOTE - PROMOTION - APPLIES FOR PERUVIAN RESIDENTS
RESIDENCE IN PERU SHALL BE ACCREDITED WITH PERUVIAN ID OR ALIEN CARD OTHERWISE AN ADDITIONAL CHARGE OF USD 178.5 WILL BE APPLIED OR BOARDING WILL BE DENIED.
What would happen if I lived in a state of blissful ignorance - are they actually enforcing this fee?
Currently the difference in price is in the region of $178.5, so a 10% chance of slipping through makes it worthwhile (low risk, high reward). Therefore it is also helpful to know, is the penalty per booking or per leg?