such a great question and I haven't given it a ton of thought yet but my gut reaction is probably $10-11 per dozen. once you learn what it takes to make your own food it kinda changes you
I'm thinking I'm coming in somewhere in the middle here. Maybe $8-9 per dozen.
My hens are a little older now though so they don't lay quite as frequently as they used to. I'm thinking with the cost of bedding and food for chicks you have kind of a steep initial cost to overcome. With that aside, under ideal conditions, I'm gonna estimate I could produce a dozen for as little as $5-6 but again that'd be growing their food, during spring, with young hens and a heavy laying breed. YMMV of course.
It depends how long you've had your setup. When you've just bought your coop, fox proof netting, onduline for the roof, tanalised timber posts, a staple gun, feeder, drinkers etc. , your first dozen eggs will look incredibly expensive!! But ten years down the line, it's a different story, when your overheads are just layers' pellets, bedding, diatom & Poultryshield for coop cleaning...
Interesting question - I'd say the cost is more than you'd pay in the supermarket. With 3-6 hens you're not going to get anywhere near the economies of scale of the big producers, particularly if you're free-range / organic. But of course, our reasoning is not based entirely on accountancy