What you said is not entirely true. Daraprim (the drug you are referring to) costs $10 out of pocket for insured patients. For uninsured low income patients it's free of charge.
My line of work makes me pretty familiar with the insurance market, there is no way a drug manufacturer can ensure $10 out of pocket, they can lobby for certain drug level coverage in formularies but where they land and what those levels translate to in terms of cost is up to the drug company, ways around this that have been tried (drug companies offering manufacturer rebate coupons to lower out-of-pocket costs) can be countered by insurance companies refusing to cover costs that a rebate would cover or refusing to cover any costs without the rebate being activated...
What you said is not an achievable statement.