I actually never looked at our chickens as an expense as they were mostly free range and their poop was composted and put on the garden.
I'll never be entirely self-sufficient and don't have any chickens at the moment. I do think we could live off of the garden for an entire year if I preserved 75% of it. Hubby feels meat is a requirement but my daughter and I could do without if necessary. I have the knowledge and ability to forage and eat things that most folks around her would feel beneath them such as chickweed, lamb's quarters, dandelions, plantain, etc.
As someone else already mentioned, one of the keys to self-sufficiency IMHO is taking advantages of surpluses when they happen. I've been lucky to have been the recipient of over two bushels of green beans because the people who planted them had their cellar full and didn't want them. The only cost was the gas to go get them and the time to pick them. In my own garden I will share some of my surpluses but usually try to preserve at least half of it as it may be years before I have another bumper crop. I actually added a 1 1/2 rows of beans because my parent's beans weren't producing very well this year and they only grow one variety. I pick and deliver them, mom cleans and cans them. If I find my own supply of canned beans running short I know there's always extra waiting for me there. I also planted several varieties of dry beans this year but its been an exceptionally wet summer and I've turned my focus to growing only for seed this year as I'm losing approximately 50% of my crop due to the damp conditions.