For your own use, there is nothing wrong with growing 8-10 pound roasters. Those are the ones I like for my own consumption. But as soon as you start selling them, you'll run up against a few things:
a) At $3 or $3.50 per pound, you start selling $30 chickens. Chicken should never cost $30 in most people's eyes, who view chicken as a cheap dinner idea which will feed a few people for one meal... not making multiple meals out of using leftovers. Something just doesn't "click" for customers that they're getting more meat, and the larger ones I bring to market always sell last.
b) The ammount of feed to go the last couple pounds puts you on an upward swinging exponential curve. The economics get really screwy and the big birds are less profitable than the 3-4 pounders. Actually, you'll be lucky not to lose money on the 10 pound roasters.
c) At my market, 3 pound birds sell first, then 4 pound birds, then 5's. People are always asking for the smallest bird I have left. I don't know if it's the $$ aspect or just what people want.
d) For ethnic consumers (mainly of Hispanic origin here), they are seeking roosters. Traiditionally, a lot of dishes are made with rooster and they still follow the customs. So big meat birds are not a niche to be going for. The niche the birg birds fit in is the married family with too many children; which often aren't spending a lot of time shopping outside the supermarket.
e) You'll probably get charges an extra couple bucks per bird from your processor if they're over 5 lbs live weight. So an extra dollar or two on a 5 pound dressed bird is adding up to $0.40 per pound of cost per beast. That's more than most people's profit margin.
