Single payer can cost less because it allows the government to solely and arbitrarily decide how to ration care, who gets things fixed and who does not, who lives and who dies.
Single payer is the exact opposite of freedom.
Example - you are super healthy 80 year old who needs a replacement knee - nope, you don’t get it - tough. Average life expectancy is just 78, so you are lucky to still be here. We’re out of budget for those, you are too old, take an aspirin instead, etc, etc. Don’t care if you want to pay for it yourself - not allowed.
Health care is not and never can be a right.
I posit that there should be two simultaneous health care systems: single payer and private, so as to allow surgery in your example. And why not? Cost to patient on single payer: zero. Cost to private citizen who has money to pay for private care: Whatever the market will bear.
“Single payer can cost less because it allows the government to solely and arbitrarily decide how to ration care”
In other words, it allows the people, through their representatives, a say in how, and how much, of their hard-earned money gets spent on other people.