I've never been told any expected cost, but I can tell you that my parents were both working, and my mother is employed by the government with a great healthcare plan. Even with that, we weren't really hurting for money, but we could rarely take any vacations or have any other luxuries of the sort. There wasn't a whole lot left by the time the hospital bills and copays were taken care of. That's why it was such a blessing when I got my SSI and Medicaid. Things are much easier on the family now.
As far as transplant costs? Let's put it this way. My mother's insurance would require a 10% copay. That alone is $10,000 (if I'm correct, which I'm pretty sure I am). My advice? Make sure your health insurance is as good as you can get, and start saving up finances now!