I added up the costs of my gardens for the past three years and tried to estimate the value of the produce. My costs have been high because of fencing my plot 3 years ago, adding the cold frame this year, and the shelves/lights last year. These will each last many years. And its hard to estimate the value of produce, because I think its worth more when its homegrown. In any case, my produce is probably valued about $500- $700/year (which is also about the cost of a yearly CSA share these days). And the garden has been costing me about half of that, even with the recent improvements: $300- $400/ year.
Of course, this summary doesn't add in my time - that would way more than double the yearly value of my garden!
I had fun reading "The 64 Dollar Tomato" recently. Its an old book by now, but I just got around to reading it. Using Mr Alexander's way of calculating, my tomatoes cost me -12 dollars this year! Does that mean I could have sold them for 12 dollars each? Hmmm. Well, that's just because I didn't pay $8,000 to have someone design and install my garden on my estate for me. I wish he had added photos to his book. I bet his garden was beautiful!