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.