Must be nice. The main cost input to eggs is chicken feed. Assume a $15 bag will keep a dozen hens fed for a month, that's about 240 eggs (assuming 2 eggs per hen every 3 days) at a cost of $15 so about $0.06 per egg. Cost will drop significantly if chickens are kept on pasture and the labor inputs for a flock of a few dozen are minimal.

It may not be enough to live on but for a hobby, it's pretty much free money. Although I assume the market charges a stall fee that will eat into profits, but still...

I don't go to the local farmer's market because it's too political, but supermarket eggs here are often under $1.00/dz (presumably sold as a loss leader) and the most expensive "certified pasture raised" eggs are about $6/dz.