It depends on the way you milk them. If you force the venom out, you can get quite a good bit. If you just let them put out what they want, you will only get 2-3 drops, maybe 5 if the snake is really in a bad mood. Snakes don't waste their venom by putting out more than they need. But if you force the venom out, it can hurt the snake's venom glands, and can cause complications. If you are milking the snake so that it will live, you don't force the venom out.