US agriculture is extremely efficient. Agriculture in underdeveloped nations is, usually, inefficient. The retail price typically only costs less because there are less steps between producer and buyer.
For example, in the US, only about 25% of the cost of bread is for the bread itself (wheat, baking, etc). IIRC, in egypt, about 50% of the retail price of bread is materials/production. Thus bread there costs 1/2 what it costs in the US. But egypt is an outlier in agriculture with an extremely high wheat yields for a nation at their economic situation. Probably due to the fertility of the nile.
seems like I've getting pretty much everything that's economically viable from the chicken, plus a fair amount of labor put into the chicken