I actually didnt get a single extra egg or chick for over 80 birds from several seperate orders this year. XD
Ideal though you want to make sure your okay with getting a different variety of the breed. They might not hatch enough and you might get say, a dark Cornish instead of a buff cornish
MyPetChicken buys from other hatcheries and resells them, sometimes with an added sexing offered. They're more expensive but I think they have a 6 minimum instead of 15 like most