Couldn't a lot of the countries that have single-payer systems negotiate better prices that more people could afford? Isn't this what happens with other life-sa

Couldn't a lot of the countries that have single-payer systems negotiate better prices that more people could afford? Isn't this what happens with other life-saving therapies at the moment? The economics of health care costs confuse me because yeah, demand for staying alive is somewhat infinite, but at some point governments seem like they should be able to tell pharma companies they can either take what's offered or get nothing at all and have the governments ignore their patents.