More often than not people have problems with $30 Petco Balls. They typically get CH snakes in from Africa which may or may not have been treated for parasites, dehydration, etc.

A reputable breeder will usually stand behind their snakes and make sure they are healthy and thriving before selling them to a customer. Usually they will make themselves available for any questions or concerns that you may have regarding your snake, and will guarantee their health. Will Petco do that for you?

For me, saving a few dollars just isn't worth the piece of mind that a good breeder can give you...