The snake will get sold eventually, and they will profit from it. I would rather it go to a loving home than it go to a home that "can't afford it" and has to return it, or just keeps it and treats it terribly.
These stores will not stop carrying poorly cared for snakes if we stop purchasing from them. SOMEONE will end up buying them. Thats just how things work. I personally don't buy from pet stores because of the outrageous prices.
OP: is there any chance you could talk down the pet store and negotiate on a lower price based on the condition of the snake?