Depends. I'll never buy from a petstore again after my ball python came with a free case of mites and was fed live mice (resulting in multiple scars that prevent him from shedding well).

If you want to go with a breeder I would suggest going to Fauna Classifieds and looking at the Boa classifieds there. They have some good deals and you can check if the breeder is reputable at the same time!

If you want to buy from a pet store...I suggest paying exceptional attention to how they take care of their snakes and animals in general. Are their tanks/whatever they're kept in clean? I'd check out the gravid female and see how she looks- does she look healthy and is she kept properly?

Just my opinion of course.