What do you think he's going to do with the money paid for the snakes? .... In my experience in this biz, theres a good chance the he's going to buy more snakes and most likely keep them in the same condition ... are you going to buy them all? ... How about his breeders, are you going to buy them too? And what about the next guy that does it ... are you going to rescue all of his "poor snakes" by buying them?
Since it's not realistic for you to personally go out and buy (aka "rescue") every single "poor snake" that is kept in less then stellar conditions, why not take a more logical route. Why not be outspoken against the practice. Why not make as big of a stink as you can to let people know that it's not acceptable to treat animals that way? Why not hold people that chose to profit from the animal trade to the highest possible standard by not supporting anyone that doesn't treat the animals in their charges with respect. I have a feeling that if more people put their foot down and said "no more" instead of looking the other way or making excuses, there would be a whole heck of a lot less "poor snakes" to buy (aka "rescue") from "shabby breeders" (your words, not mine).
Just some food for thought.
-adam