So far, the costs outweigh the benefits
At this point in 2014, my garden is costing me more than it's saving me. I've been trying to keep track of everything we eat from the garden, (via the freezer or the canning shelf right now) but I'm pretty sure I've forgotten to record a few.
I've already ordered seeds and paid for my irrigation water for the 2014 season. We would pay for irrigation even if we didn't have a garden, but I figured since I use it to water my garden, I'd charge half of the yearly cost to my garden. It's irrigation water, so even though it was twice as much as its been in the past due to capital expenditures, it was still only $106. Not bad for all the water I need in my garden for six months.
My year-to-date costs are $141.65, which doesn't count some seeds that I've ordered, but haven't actually paid for yet.
I didn't start keeping track of the produce I've used until the middle of January, but so far, I estimate that my garden has supplied me with $49.47 worth of produce. Not bad for half of January and February.
That means that my garden has cost me $92.18 so far this year. I'm pretty sure the pendulum will swing the other way once I actually have things growing outside in the dirt, but I plan on continuing my garden cost calculator throughout the year just to see.
Of course, I can't calculate the value of my mental health, which is greatly improved every time I look at a seed catalog in the winter or go for a garden stroll in the spring, summer and fall.