Free markets provide the optimum (lowest cost) solution when certain conditions are met- like both parties to a transaction having perfect information.
Commodities are the ideal case. Shoes, cars, etc. You can compare exactly what you are paying versus what you are receiving and make your decision. The free market works brilliantly in cases like this.
With healthcare, the provider doesn’t know what services they will be asked to provide in the future, and you don’t know the quality of service you will receive. Both parties enter into the agreement essentially blind. The lack of information on future services and quality of those services creates an inefficiency. This is why the free market model breaks down in the area of healthcare. Not enough information.
Free markets are a remarkable tool for driving down costs and increasing quality, but they are not a one size fits all solution. Although many politicians think otherwise.