A lot of the expensive eggs are more than just organic. There are other classifications for eggs too. Like cage free, or free range. These have increasingly strict regulations (for now I guess).
But free range chickens must spend a certain amount of the day outside, and below a specific population density for that range they are free in.
Cage chickens can't move and shit right next to each other. They are more likely to get the flu I believe.
I think the word you're looking for is deepity.