Higher prices for visits to doctors, surgery, and drugs were the main cause of higher health-care costs for privately insured Americans in 2010, when overall utilization of health-care services was down, a report by the Health Care Cost Institute in Washington, said Monday. The report, using data provided by Aetna, Humana, and United Healthcare, analyzed three billion claims for 33 million individuals covered by employer-based health insurance from 2007 through 2010.