Many vegetables can be expensive to purchase by growing the most expensive vegetables in your garden and buying the least inexpensive vegetables at your grocery store you can easily help drop your food budget. This especially important for people like me with very limited space to grow everything that I consume.
It may be impossible to put a price on the satisfaction of bringing in a basket of produce fresh from your garden. As well as the enhanced flavors from having truly fresh produce from your garden compared to that of your local supermarket. Though when I was harvesting my potatoes this summer with my daughter I did have the thought, Would it have been smarter for me to grow something else in this space? I estimate out of the 4-5 square feet I used for these plants I probably got about $4-5 worth of potatoes.
I did a little research first to determine yields of various plants per square foot and secondly what the value (organic supermarket prices USD) of the yielded produce at harvest. Given I am a city dweller with a fairly small footprint for my vegetable garden (about 30-35 square feet) making decisions on what to buy at the supermarket and what to grow in the garden may be a huge money saver with just a few dollars invested in some seeds for your vegetable garden
Now from the results below you can see the winners for the most produce value per square foot are many of the leafy green vegetables/herbs (cilantro, lettuce, chives, dill, Swiss chard) next comes many of the larger vine plants (tomatoes, squash, pumpkins, peas) with many of the root plants taking up the rear. Now much of this makes sense where many of the vine plants grow on trellises and are allowed to spread, which I guess is sort of cheating the square foot rule but I will let it slide. Compared to the root plants whose production is entirely dependent on the space allowed in square footage they have to grow as well as these are normally inexpensive produce items to begin with.