"Emergency care can't be a free market" is a reasonable statement provided the customer is the patient and not e.g. an insurer with a contractual obligation to meet a particular emergency response time, who could contract with different emergency services providers in any given area in advance and secure lower pricing by playing two providers who could each meet their emergency response requirements against each other or threatening to enter the market themselves.

"Joint replacements can't be a free market" is simply nonsense.