It depends on what others in your area are charging. And it is not clear if you are selling hatching eggs or eating eggs. Unfortunatly you need to look around your area and do research. Go to the feed store and ask or look at bulletin boards. For eating eggs called farm eggs you can charge from $3 to $8. For hatching eggs folks charge more for a dozen, maybe $15 to $25 if there is tons of folks who want them. Look to see if there is a specific thread for selling eggs on BYC.
Also look to see if there is a thread for your state and see if anyone can tell you what they charge.