Doubtful that eggs were expensive on terms of cost per calorie compared to chicken.
A 4 pound chicken will get you about 2000 calories after it is cooked, whereas the same chicken would lay approx 5 eggs/week, each @ 75 calories, or 375 calories/week. So, it would only take 6 weeks for a chicken to output as many calories as exist within it, and chickens lay eggs productively for 4-5 years.
