Comment by sepositus
We have 10 (backyard) chickens and spend about $40/mo in feed. We average about five eggs per day when they are laying, so let's say that's 150 eggs per month. That's $0.26/egg or $3.20 a dozen.
But we have to factor in around 4 months of them not laying during the winter. So for laying months, that brings the feed price to around $60/mo or $4.80 a dozen.
So yeah, at current prices, it's worth it for us. I also haven't factored in the value of their compost, which is really quite expensive when you're buying as much as they generate, so it's probably even cheaper than listed.
FWIW, you can get generally better results with different breeds. Golden Comets or ISA Browns will typically get you 1 per day per chicken. In reality if you had 10 you'd likely get 8 or 9 per day. They also seem to lay in the winter better than many. Unfortunately they just don't live long so it's a constant cycling process.