I saw those recently on their website.
The chicks from tractor supply and other feed stores are not usually good quality. I've bought some before and they all had the feather shredding gene...so when they were grown they looked like they had a silkie tail. Their body shape was too lean also. The ones on Craigslist probably had been bred to a better standard so therefore would be better quality. As in most cases you get what you pay for