I have taken people to places where they pay with their credit card and almost get a heart attack.
Remember that we are in Mexico and the currency is the Mexican Peso. That means that when you get charged, you get charged in Pesos not in dollars, so that means that your lunch bill was not $700us it was $700 pesos.
When you get your bill back home, you get it converted in dollars. I have heard from many people that actually your bill is even less, due to the international rate of exchange.
Just so you all know........