I did a little research first to determine the different cultures of plants per square meter and second, the value (organic supermarket prices USD) has to produce the crop. Because I'm a city dweller with a relatively small space for my garden (30 to 35 square feet) make decisions about what to buy in the supermarket and grow in the garden can be a money saver.
Now from the results below you can see the winners to produce more value per square meter, a lot of vegetables / herbs (cilantro, lettuce, chives, dill, chard) next, many of the larger plants tomato vine (squash, pumpkin , pea), with many of the plants roots take up the rear. Now much of this makes sense, where many of the plants that grow on the vine trellises and allowed to spread, which I think is kind of cheating a square foot rule, but I'll let it slide. Comparison with root plants whose production is completely dependent on the space allowed in the area that has to grow, as these items are generally cheaper to start producing.