Single payer largely avoids unpaid bills and a great deal of bureaucracy around billing. This is true even in the US, just look at the VA’s costs. The VA is serving a very expensive population and it does so relatively cheaply for the US. At least in terms of services rendered rather than just per person.

The 24/7 comment was in comparison to dentistry. It’s tempting to compare getting stitches to getting a filling but inherent overheads are associated with an ER which must be added to the bill.