Life-saving drugs that can combat cancer or hepatitis C have grown increasingly expensive. More than 500,000 American homes spend $50,000 or more on prescription drugs. 139,000 Americans paid over $100,000. How is this happening?

A new report by Express Scripts published on May 13, 2015 brings light to the issue.

“Among patients whose drug costs reached at least $100,000, more than one-third of these patients were being treated for ten or more different medical conditions. The most common co-morbidities included high blood pressure, high cholesterol, diabetes, and depression. Approximately 60% took 10 or more different medications.”

The report examined the profile of these drug users and found that the majority were aged between 51 and 70. Also, men were slightly more likely to spend over $100,000 on medication than women.

“The profile emerging from this research shows these patients are overwhelmingly taking specialty medications, and have multiple comorbidities, prescriptions and prescribers,” said Dr. Glen Stettin, senior vice president for clinical research at Express Scripts.

A look into the costs of these life saving drugs reveals how medical bills run up so high.

Gilead Science’s Sovaldi, which can cure a person of hepatitis C in three months, costs $84,000 for the regimen. The pharmaceutical company argues that the fee is less than the cost of lifetime with liver disease.

Bristol-Myers Squibb’s Yervoy, a drug that can keep terminally ill melanoma patients alive for over a year, costs $120,000.

And who pays these exuberant fees? For the most part, insurance companies. “Insurance plans and employers covered more than 98% of the costs for patients whose prescription drug bills exceeded $100,000 in 2014, paying an average of $156,911 of these patients’ 2014 pharmacy costs,” said the report. The two percent that patients were obliged to pay out-of-pocket was on average $2,782.

These figures of course apply only to those with top tier health insurance coverage.