Insurance pays the higher of their negotiated rate or the billed charge. Medical facilities set their billed rates so high that they’re guaranteed to be higher than all negotiated rates, ensuring that they get paid.

When you see $37 aspirin on the line, nobody actually pays $37 for it. The billed amount is replaced with whatever insurance rate is allowed for that. If someone is cash paying they get a large discount.

The billed items also have to cover everything. It’s not directly $37 for the aspirin, or the $5 or whatever allowed coverage it ultimately gets billed it. That had to cover the facilities, the salaries of the pharmacy staff who reviewed the request and dispensed it, the staff who inventory and order the medications, and the cost of billing insurance.

The only part that nationalized health care would change are the allowable billed rate and maybe the administrative overhead of billing different insurances. Even nationalized health care systems have admin overhead though.

You can think of it like when you have to pay $11 for a single glass of wine from a bottle that the restaurant paid $10 for. You’re not just paying for the liquid, you are paying into a big bucket of charges that all need to add up to more than the cost of the supplies, staff, building, and everything that goes into running it. The margin on individual products doesn’t make the entire operation profitable.