First let me say it's very complicated.
Depends on your plan. I'm going over the healthcare.gov site right now. Some plans offered to me have better coverage but at a higher premium (premium = monthly payment). The higher the premium the lower the deductible. Obviously, people with bigger health issues would select a plan with a higher premium and lower deductible because they offer more coverage (like 90% coverage of name brand prescriptions with a Blue Cross-Blue Shield plan). Somebody like you or I would get the cheaper plans from Humana. (basics with almost no coverage but emergency situations).
Bah, forgot to answer the main concern. If your operation for example costs only $2,000.00 and your premium is $6,000.00 the insurance will cover it with conditions. The conditions vary from plan to paln, such as $40.00 flat rate doctor visits, etc.