Chris Hedges' article at Truthdig provides the following data points from Harpers 2009 Index
Percentage change since 2002 in average premiums paid to large US health-insurance companies: +87%
Percentage change in the profits of the top ten insurance companies: +428%
Chances that an American bankrupted by medical bills has health insurance: 7 in 10
—Harper’s Index, September 2009
From personal experience I can tell you how insurance companies make their money--by denying medical services. My insurance company refuses to cover the latest treatment for migraines, despite my clinical history of chronic migraines (at least 15 a month) and the failure of conventional migraine treatments.
My insurance company also routinely takes 6-12 before they will make payments for medical procedures. For example, after 12 months they still had not paid for an MRI conducted at one of their approved provider sites and ordered by one of their approved physicians.
I believe the market is the not the best mechanism for providing health care because the profit incentive undermines care and quality.