I've recently begun selling eggs, because we have way more than even our family of 7 can consume!
Like others have mentioned, I go with a fair price - $6/ dozen with my nice carton, $5/ dozen for refills or BYO box. Free range organic eggs in the grocery stores here go for $8-10/ dozen, so I'm giving people even better quality product than the free range store eggs, for not much more than they'd pay for horrible battery farm eggs.
I don't wash my eggs, I just dust them with a dry cloth and sell the most cosmetically appealing ones without poop (let's face it - poop happens, even in the cleanest nesting box!

). I also label my cartons with a little blurb about them being fertile & unwashed, what the bloom is, how farm fresh eggs are different from store bought, how they're collected daily and how happy the chickens are, etc. And I include the FDA safe handling instructions just to be sure it's all "legal"... always CYA, especially since our ranch name is on them!
My next project is to take good photos of all my chickens, and include a "chicken of the week" card with a funny bio of each in the egg cartons as an extra cute touch.
So far, I'm only selling to family & friends who actually appreciate the quality of eggs and how I care for my chickens. And in turn, the income from selling eggs pays for my chickens' feed & care. It works out nicely!