It's quite impossible for a backyarder to out-compete commercial agriculture on price. If it were possible the commercial people would adopt backyard practices.
For example, I can regularly get 40# boxes of miscut chicken for $20 at Piggly-Wiggly (this is not necessarily possible in places that don't have Perdue plants nearby). The quality isn't the greatest, especially because I have to thaw it to portion it out and then refreeze it, but for 50-cents per lb I accept that quality.
To save money with your own meat birds you have to be comparing your chicken to high-end, pastured, specialty poultry rather than the ordinary chicken from the grocery store. Our home-raised chicken is, we hope, far superior in quality, but it's not saving any money unless you attempt to buy the same quality.
Garden produce is a little more forgiving, but I don't raise cabbage because I can't save any money with it. Cabbage is only 50-60 cents a pound, after all, and takes a lot of work spraying and/or keeping it covered to prevent the cabbage moths from destroying it.
Beefsteak and multi-colored cherry tomatoes, however, pay off.
Likewise pickling cucumbers and winter squash -- assuming I have the space available.
Well said.