I think it depends on your personal preference. Last year we let four of the meaties go to 12 weeks, not because we had planed it but because things got crazy around here.. When we did butcher they weighed in at 6.5-7.5 pounds packaged!! That's a lot of meat, more than either of us wanted.. This year we checked them at six weeks, decided to let them go one more week. Butchered all 18 yesterday and they are ranging from 3-3.5 pounds butchered weight.. Much happier, typically its just my husband and I for dinner so a smaller more manageable meal is what we are looking for, its enough for dinner one night and left overs the next.
Yes, its about the size we would buy in the store and when we factored in the price we paid for the birds (.75 each) plus the feed 200 pounds at 15.50 for 50 pounds they came in at roughly $4. each, BUT they were raised on our farm , I know how they were kept and what they ate so getting "more bang for our buck" wasn't so much an issue