If selling chicks, they are selling the potential to be show quality, based on years of line development and reduction of disqualifying flaws. There are no guarantees that they will be better than pet quality, but the odds of getting an exceptional bird are increased dramatically over purebred hatchery birds.
I don't show birds, or sell chicks or hatching eggs intended for exhibition, but I would still invest in the best stock possible if I were raising pure varieties.
There is at least one big commercial hatchery that claims to have "blue Ameraucana" and the way I read their site they are asking $16.96 for straight run day-old chicks. I don't know of any breeders that would charge that much though.
It does make a difference if shipping is included and it can cost up to around $45 to ship a box of 25 chicks using Priority Express Mail, depending on distance.
Once you buy the birds it costs the same to feed and house a cheap one as is it does an expensive one.
I do believe "purebred" for all the Standard traits is nearly impossible to achieve and that is why I prefer "standard bred".
Point taken on "standard" vs "pure". Your AKC analogy is a bit off the mark as dogs must be pedigreed to show, poultry not so, the genotype does not seem to matter as long as the phenotype is correct. It's interesting to read historic breed SOPs dating back to the early days of the breed, and today's, or to view old show photos of champion birds. I can't say that all the changes made to what were for the most part useful fowl have been for the better of the breed as a functional bird.