Also what age did you slaughter them? How did you feed them?
Back when Delaware were bred to be meat birds, 50 or more years ago, a good strain would reach 4 pounds at 10 weeks when fed a meat bird diet. With extremely few possible exceptions, they haven't been bred as meat birds since the development of the broilers. If the person selecting the breeding stock doesn't select for certain traits like weight gain, the flock quickly lose that trait. No hatchery is going to breed for rate of weight gain. Very few breeders will either, they are more likely to be looking at the finished product for "show quality" traits, the things the judge sees. But that can vary tremendously too with different breeders.
You can't compare hatchery chicks with breeder birds. The hatcheries are breeding for the mass market, not show, and their prices reflect that. Different breeders are going to be breeding for different things too. You need to know what you want and if the specific breeder is breeding for those traits.
The OP saw the birds that produced those eggs and hopefully had a chance to chat with the breeder. There is an outstanding chance they will be really happy with what they hatch.
