The health care costs in America are going up for many reasons.
One: Patients are requesting test that they do not need. ("I would like an MRI") They request these even if the doctor says they do not need one.
Two: Malpractice Insurance. If the doctor in the above answer refuses to give the MRI above and the person has the unlikely problem that the MRI would have caught, they are sued and have to pay more malpractice insurance.
Three: Lawsuits. Doctors order more test to cover themselves because they may be sued, thus increasing their cost. This is why some people are pursing for a "loser pays" tort reform.
Four: Technology. The U.S. does a lot of research in medical care. We have to use these new procedures otherwise; you cannot justify the cost of the research, thus raising the prices of health care. New always cost more.
Five: Interstate commerce. Insurance companies cannot sell insurance across state lines; therefore, they must open locations and navigate bureaucracy in every state before they can sell insurance there. This cost money; hence, your cost goes up.
Finally, the nature of insurance has changed. It used to be used to "insure your" against costly procedures, i.e. I feel off a ladder and have a compound fracture in my leg. Whereas now, people think of insurance as I can pay this monthly insurance premium and go to the doctor whenever I feel it necessary and I will only have to pay $30.
These are not all the reason, but the ones I could think of off the top of my head.