Grocery shopping at the calories to price ratio

When I'm shopping for food, I'm focused on two things. First is, obviously, acheiving a balance in nurtient and carbohydrate/fat/protein content. The second focus is on the calories to price ratio. If you're not careful (especially at the natural foods grocers), you can end up buying a lot of things in the 100:1 area (100 calories per dollar) that also don't have any special nutrient content. My goal is generally to average a 600:1 ratio. This is nearly impossible if you go around the isles only picking up prepackaged foods, but there are options, such as potato chips, that are in that value range. The place where value really shines is in the bulk section, where one can find deals upwards of 1000:1. However, most of these foods are carbohydrate-rich grains. Two things that you undoubtedly pay a higher price are meat-based proteins and nutrient-rich vegetables. This can be offset with vegetarian proteins such as beans and nuts and careful selection of the right vegetables. The good news is that we don't need as many grams of protein as we do carbohydrates. For instance, 2 cans of tuna fish can be had for $2, and while is only about 300 calories, it is a day's worth of protein.
Being a conscious shopper can help one be healthy while still only spending under $5 a day on food.