Mexicana in Mexico does NOT care about you. They were greedy, money-hungry, rude, and totally unprofessional.
They left my family to sit on the floor (provided no chair) while we waited over 6 HOURS trying to board a flight on our paid tickets. When I got fed up and couldn't put up with their comedy, I went to another city, another airline and finally flew back home.
Though they may come off as selling tickets cheap, don't be surprised if you lose it because of their slow or sneaky services and you have to pay all over again.