Consider the taco an element, like boron or lead or molybdenum. Beans, cheese, lettuce, guacamole, sour cream -- such abominations correspond to a taco about as much as wasabi beurre blanc does. A soft corn tortilla, meat -- lots of it, gum-tender, and highly seasoned -- and a dollop of salsa, preferably one with a kick to it, are all that compose a proper taco. And Rosita's turns out proper tacos. You can get three of them -- shredded beef (the best), chicken, and chorizo and potato -- plus rice, refried beans, and a small tomato-lettuce salad for $6.50. That is about as cheap and elemental as you can get, especially considering the price of a three-fer of molybdenum these days.