You can buy normal BP's from breeders for cheap (they don't list them on their website, but if you email them they can hook you up)
Buying from petsmart has a few major issues.
1. Cost, they charge way to much for a normal BP
2. The health of the animal: petsmart keeps their reptiles in terrible conditions (improper heat/humidity, and they don't feed them enough, or even the right things)
3. Wild/captive hatched: most pet stores sell snakes captured from the wild or eggs taken from the wild then hatched in captivity. You always want to get a snake that was conceived and hatched in captivity. If you get one that wasn't, they generally have a bad attitude, they are harder to get to eat, and have a high chance of internal parasites.