well there are many reasons to why it is expensive but I onlyknow one, and that is that the animals that you have selectivelybred may have consequences to the genes it has inherited. Forexample, in a cow, there may be a gene that produces more milk andso people breed cows of those specific genes. However, there may bea gene that is inherited WITH this feature, likemastitis(inflammation of the udder) which means that there would bea lot of money spent on treating every cow of this illness who hasthe feature of producing more milk. Get it?