Chicken poo makes a great fertilizer too.
Commerical organics are more expensive as they don't get the yield as regular commercial foods (which are in no way un-healthy for us). They lose yields to weeds, bugs, fungus, rot, etc. It's a marketed ploy to jack up prices for the most part.
I have nothing against home gardens -- but then we always used to sprinkle powder on our cabbage to protect from moths/butterflies and we had a problem with potato bugs, smut in corn so technically we weren't organic either.