You still don't understand. The total level of benefits and taxation is relevant. Healthcare doesn't exist in isolation. For example, you can pay doctors a lot less because they go to medical school for free and don't have malpractice insurance at the same level and also because their retirement is taken care of by the state. You can pay hospital administrators less and on and on. This lowers the accounting cost of healthcare - but not economic cost. Somebody paid taxes to send that doctor to medical school for free
This high overall taxation enables subsidies which are then used to make it look like healthcare costs, when looked at in isolation, appear lower.
Empirically, we can see this: very few developed ountries are able to provide lower healthcare costs than US while also having a lower overall taxation burden.
Oh. You are thinking of secondary effects of high-tax societies, such as flatter wage structures influencing (production) costs of healthcare. Yes - I absolutely agree that is a factor, and I genuinely believe that if the US wants to see the full economic benefits of single payer they must also make higher education cheaper, reform the malpractice legal frameworks, and so on. The fact that I tax-pay my doctors MD likely makes less of my tax money go to healthcare. Agree.
The UK does have a good single payer system and not (entirely) free higher education, so they naturally have more wage inequality (for other reasons as well including much weaker labor unions and labor laws) and should be a better comparison than e.g Scandinavian countries which has flat wages and tax-funded everything. Canada seems similar (tuition there seems to be around 50% subsidized?)
This high overall taxation enables subsidies which are then used to make it look like healthcare costs, when looked at in isolation, appear lower.
Empirically, we can see this: very few developed ountries are able to provide lower healthcare costs than US while also having a lower overall taxation burden.