Having said that it's not just the income of doctor. Healthcare administration is expensive in the USA. Many doctors offices spend a non insignificant amount of money on just the billing, collection, insurance administration. The health insurance system as we naturally ended up with sucks up a non insignificant amount of money out of the system. It also leads to these weird distortions where every insured procedure is discounted to the insurance agency like 75%... But not if you deal direct.
Additionally, operational insurance (malpractice indurance) is another non-insignificant contributor. Our culture and our legal system ensure that many doctors practices will pay a multiple of a practitioners salary in malpractice and related salary.
If we want cheaper healthcare all of these need to be addressed one way or another. I am not hopeful that we can escape this local maxima that we're stuck in. Every attempt at change will be meet with fierce opposition from the current status quo.