Sometimes I think I should change the name of this blog to reflect my favorite food: Oatmeal. Recently perusing the New York Times I found an article for Healthy foods for under $1.
Number ONE on the list is, you guessed it, oats: "High in fiber and good for cholesterol. A dollar buys you a week’s worth of breakfast or keeps you well-supplied in oatmeal cookies."
In Buenos Aires, Oatmeal is not difficult to find; the challenge for me was obtaining the old fashion style rolled oats (avena gruesa). Going to the dietetics stores in your neighborhood and asking for this product will help you figure out which stores consistently carry it.
I was fortunate enough to find Willy, a native Bolivian who has lived in Argentina for many years (he's a Tango teacher) and is the owner of a natural food store a block from my house on the corner of Juncal and Ecuador. For 5 pesos, I get a large bag of rolled oats that generally last me a week (but that is calculating that sometimes I consume it twice a day, and rarely does a day go by where it is not enjoyed).
Also, at his and other neighborhood stores, take advantage of getting other products you find on the NYT $1 list and my own personal cheapy favorites: peanuts, raisins, bran, yogurt and Tofu.