I pay .35 cents a lb for chicken feed and I think the bag of bird seed was around $3.45 at Walmart, so yes its definately more expensive.
I got some eggs from a lady who has chickens and about four of her eggs broke as soon as we picked them up. I am sure she's not feeding them greens, we saw them and they were just looking for worms and grass. And I don't think she gave them oyster shell or grits because the eggs broke so easily. She sells her eggs all the time. I want to have healthy eggs that are good and strong and anything I can do to achieve it I will. I try to feed them greens, either cabbage, lettuce, kale, squash or weeds and clover at least twice a day. Its not alot because there only 6 weeks old but they love it and I know that they're growing and will produce the best eggs possible.