The only thing separating you from eating sustainably on the cheap might be a nice, sharp blade -- and the knife skills to use it.
Cooking at home -- from scratch -- makes it possible for many of us to afford to eat local and organic foods. But the No. 1 barrier people have to cooking at home is time. And, for amateur cooks, following recipes is much more time-consuming without strong knife skills.
The more capable you are in the kitchen, the more flexibility you have when it comes to buying and eating whole, less processed (often more affordable) foods. For instance, two people can get three meals out of one whole chicken for about the same price as buying two pre-cut boneless, skinless chicken breasts. (Of course, the vegetarian equivalent may not apply exactly, but you'll eat more veggies for your dollar if you're comfortable cutting and cooking them at home.)