A lot of the very high health-care costs can be attributed to the excessive malpractice suits that we are increasingly seeing. This results in "over-defensive" or "cover-your-ass" medical practice - everything gets checked, double-checked, no matter the cost, and no matter whether it actually makes a difference. Doctors are increasingly checking for everything, because they don't want to get a suit for missing the diagnosis, even if the diagnosis is irrelevant.
For example, FBB gave the example of supposedly having had an MRI after a concussion. I cannot think of a genuine reason why an ER doc should need the results of an MRI to make a decision. An MRI is expensive, costing around $400-500. A CT scan would tell an ER doc everything they need to know for $100. The MRI could be reserved for those few cases where the symptoms don't match-up with the results of the CT. Yes, the MRI provides more detail. But how will that actually change things? The vast majority of brain damage in concussion is invisible to MRI, but will still cause symptoms. If the MRI shows minor damage, that's interesting, but not particularly helpful, as the symptoms are a much more sensitive indicator. Yet, in many places, MRI for concussion is now pretty standard practice, because it reassures the doc that they're not missing something, and makes the patient think that they are getting top treatment.
And it then becomes a vicious cycle - as more docs think it's appropriate, more malpractice lawyers will see not doing it as negligence, and suddenly everyone is covering their asses, and costs are spiralling.