As previously stated, if you just buy it now because you feel bad for it, it just encourages the store to continue it's current treatment and setup of it's snakes. You will be rewarding bad behavior, which will just encourage the behavior to continue.
I think you'd be better off talking to the store owner/manager and seeing if you can get him/her to change the snake's environment. Some stores are cheap and treat their snakes like crap cause it's cost effective, but some are just not knowledgeable and think they are doing what is right for the snakes.
If they can get it in a better situation it'll be healthier and someone else who actually wants it will buy it and get an animal in better condition. More upside is future snakes at the store may get better setups as well.