The lowest medical costs occur in countries with single-payer government run systems. These countries also score among the highest in the world for quality of care.
The US system is the most expensive in the world. The problem is the private insurance companies. Medicare and Medicaid are run with a 2-3% administrative cost (including salaries) whereas the typical insurance company has administrative costs around 40%. This is before you even look at the amount of profit the companies take out of the system (typically massive as well). The problem is even the small to medium insurance companies end up with a board of directors and a not insignificant executive board either. Those salaries have a huge impact on insurance cost. All said and done about half of what you pay for insurance actually covers the cost of the insurance plan, and most deals with profit and the bloated administration that medicare and medicaid prove is not needed.
In addition the current system has insurance costs rising faster than health costs as companies attempt to pad the bottom line.