Not to say that the ridiculous cost of medical care in the US is mostly driven by the desire to increase the profit margins of the insurance companies, but medical education also plays a very interesting role.

Most medical schools are university-affiliated and are proud of being very well equipped. One result of this is that medical students are taught that CTs, MRIs, EEGs, EKGs and so forth are standard/normal diagnostic tools and wouldn't consider a medical workup on a patient to be complete without them. As a result of this, they generally won't go to work somewhere after their residency is complete if these aren't available to them, which forces their prospective employers (and a very large number of physicians, especially new graduates, are "employees" rather than having an independent practice) to either own this very expensive equipment themselves or have it available on a contract basis. And of course, to complete the circle, once you have it you are going to use it and bill accordingly.