This past Sunday, I walked through the weekly open air market in Copacabana. There is one each Sunday, and another on Thursday. Venders sell fruits, vegetables, meats, flowers, and more. I spent about 10R, which is about $6US, and got sardines, strawberries, 12 bananas, and coconut juice. The prices are much lower than what you find inside grocery stores in Copacabana.
What I realized was that a single person could buy enough food to survive on for one week in Rio for about 20R-30R. Of course, this hypothetical person would still have to buy water and a few other essentials from time-to-time, but one could certainly purchase enough fruit and meat to last over a week. I now perceive how Brazilians can afford to live in a nation that over the years tends to suffer from fairly high prices relative to the average income.