The capital costs for an MRI, while large, are not the biggest part of the price. I had an MRI done in Pune (with a good machine, 3T/32 channels) for 6500rs/$130.
Labor costs are a biggie. In the US, you need to pay technicians high US salaries, in the $60-70k neighborhood from what I hear. In Pune, the technician is almost certainly poorer than 95% of Americans. The high ratio of capital costs/labor costs also causes higher utilization of the MRI - in the US, many MRI places are 9-6, I had my MRI done in Pune at 9:30pm, and someone went in after I finished.
Labor costs are actually a much bigger deal than GDP figures would suggest. High skill individuals get a much bigger premium in the US than most of the rest of the world. A top 1% person in the US gets $384k/year, in Canada only $181k.
http://www.statcan.gc.ca/pub/75-001-x/2007109/article/409688...