Pet shops, the good ones.. (the bad ones I'm not getting into at all since I would not consider that an option for a snake, or anything)
are there, I think, to offer snakes to those who don't care about pricing.. are about impulse buying (which can go along with the not caring about price), and those who just don't know better.
Like someone just getting into snakes. who care, but doesn't know until AFTER they spend $150 on a normal BP that they could have gone to a breeder who has excellent stock, and gotten a normal for a fraction of that.
Shows consist of ppl in it for the love of the animals for the MOST part. People who do it because they like working with different species,morphs,etc..
and they cater to those same people. people who are knowledgeable (for the most part) so for the most part, animals at shows are going to be at very competitive prices. They'd have to be, because breeders/collecters will be there that know their stuff and aren't going to pay 300x the "going rate" for something.
In a pet store, someone is going to come in and purchase that $150 dollar normal BP in a heartbeat because it's their first snake and they've done no research.