He might not have anything. You can always take him to a vet and have him checked out. The Qt is just to be safe. Just in case he does have something its better to keep him away from your other snakes. So they dont get it to. Ive never had a snake that I put in Qt that has ended up being sick. Its just to be safe. Since you got him from a petshop its a good thing to do. Where he came from, how the breeders that hatched him kept there animals. You never know someone could have came in the shop they have snakes, they have mites or something. They ask to check out the snake they pass it onto him. Yeah 50 sounds like a good price.