Well the diagnoses for your vehicle come from a 200 page Haynes manual, your body doesn't exactly have a Haynes manual for your make/model/year.
How does the complexity of the human body come into play after they've done their procedure and still can't tell me how much I will be paying?
Do you take your car to the mechanic, get some work done, only to get a bill 3 months later?
Even for a checkup, after the procedures are done, the office can't tell me the bill.
...yet we we call mechanics "wrench monkey" in a demeaning manor.
BTW, this is probably why services like Minute Clinic are getting popular...go in, get something done, pay a flat/low fee.