According to the Associated Press, the National Gardening Association claims that growers can expect a $500 return each year from their vegetable patch. Roger Doiron, of Kitchen Gardeners International, counted all the produce coming from his own (1600 square foot) garden, and valued it at about $2150.
So can you expect to save $500 to $2000 by planting some veggies this year? Most gardeners should take these numbers with the proverbial grain of salt. There are many factors to take into consideration. Cold-climate gardeners have short seasons, and the varieties we plant may be less productive (although earlier).
Another thing to keep in mind is the size of your garden. Seeds often come in packets too large for a gardener with a small plot, so the expense is proportionally more for a small gardener than for someone with a large garden, who can also take advantage of bulk pricing. Most seeds will store over several years, but the initial expense can be more than you might think.
Less experienced gardeners should be moderate in their expectations, and even experienced gardeners may lose large amounts of some crops to animals, disease or weather. The other problem that beginning gardeners face is that there are a lot of tools to acquire before starting out! Most gardeners can probably get by with a shovel, a rake and a couple bags of compost, but if you want raised beds or need to seriously amend your soil, it could be quite expensive. Even container growing means buying containers and potting soil. You can often use recycled containers (try five-gallon buckets, sometimes available from fast-food outlets, and drill drainage holes in them), and mixing your own potting soil can be cheaper, although it is quite messy.
I think it's great that a lot of people want to grow their own food. However, these claims make gardening sound like a sure thing, and I'm afraid they might lead to some disappointed gardeners. And disappointment leads to gardening that feels like a chore, and gardens that are quickly abandoned once good times return.