Demand for health care is inelastic which makes it mostly immune to market forces. With health care consumers really don't have a choice. Either they pay whatever price is set by providers or they die or become disabled by their condition. Whether the procedure costs $5 or $5000 is irrelevant. When it comes down to saving your life you will take on any expense.

More nefariously (and a point that many people often miss) recovering from a major illness is a full-time job. People who are very, very sick don't have the mental concentration or energy to even do a desk job. And if the job involves manual labor they're even more screwed. Strenuous physical activity during an illness can exacerbate the symptoms and kill the patient. Even having to stand for eight hours can greatly harm outcomes. So sick people have the worst of both worlds: accruing enormous expenses for incredibly pricey life-saving procedures and drugs, all while having their earnings drop to zero.