We love keeping chickens. I think we pretty much break even...more or less. We keep 12-15 hens and a rooster. In the main laying season (spring!), we might get 10-12 eggs a day, and DH takes the extra dozen to work to sell. We use organic feed, spend about $50/mo on it (Canada, prices extra high! :) ) and sell to a city clientele for $5/doz when free-range organic here at the grocery store are $7.50/doz. We found our neighbours around here weren't very interested in paying $5 when they can get local, free-range non-organic in this rural community for $3.5, but we do fine when taking our eggs to our more urban work settings.
So in peak laying season, which lasts for a couple of months (mid-Feb - mid-April), we're rolling in eggs, even giving them away to anyone we can, just to move them along. Then, in late spring, our heritage hens decide they really want to hatch out chicks (they go "broody"). From then until fall, we have at least 2 hens on strike from laying rotating in and out of the "chicken jail" where we try to re-program them to go back to laying. We also will sometimes get some hatching eggs and hatch out a new batch of chicks to keep ourselves in relatively young, productive hens. So through the summer, between broodiness, heat, and the older age of a component of our flock, we might get 6-7 eggs/day from our flock of 12-15.
Then, come late fall (Oct-Dec), those hens more than 1 year old go through a molt, replacing all their feathers. It's a very entertaining process! But the hens don't lay while they're molting. So production goes down again (although sometimes there's a few weeks back up to peak production between the end of the broody season and the beginning of the molting rotation), maybe 5-6 eggs/day.
As the days get shorter, many people use lights in the coop to keep production up; we don't bother. Young hens lay reasonably well through the first winter, so we just get by with 1-3 eggs/day in the winter, and enjoy them ourselves. Come the longer days of late January, like now, we're back up to 3-5 day, and are just starting to sell a dozen or two a week again.
I did track my eggs/sales for a year or so, just to see what the numbers said. I think they basically worked out to us getting most of our eggs for free, or certainly less than we would pay for them otherwise. That does NOT include the coop or other infrastructure; that's going by feed costs only.
Keeping chickens, besides being fun, has been an excellent lesson in working with living systems and why economics are tricky with them. On paper, it's a pretty simple calculation of x number of birds= x number of eggs, but in practice there are a million unexpected variables. We cull and eat our stewing hens, as well as any extra roosters we hatch out as we replace our older birds. We were vegetarian when we started on this journey, but soon it became clear to us that if we were raising birds for eggs, it only made sense for us to eat them as well--that's the way the system operates. (This doesn't mean any specific person has to eat their own birds, of course). At least one of our hens, though, we have decided is a pet, and she will live out her life with us regardless of her laying. Her name is Hen. ;)
As a last note, there are two of us and we only really eat 1 doz or so eggs a week. So this was never something that was going to save us a ton of $. That said, chicken keeping has been part of an amazing journey of buying less and food at the grocery store, and it's amazing how much our habits have changed over the last 4 years that way. It's an enriching process in many ways--some even monetary. :)