Given that health care needs to be rationed (as it's turned out it does), it still seems to me the best way of rationing is on the basis of need.
The worst way? Price/ability to pay.
In the end, this is a matter of morality. And, yes, to be sure, there will be some cheaters/queue jumpers ... but we need to try and minimise the incidence of this, not encourage it by formalising a pricing model of care.
Yes, I could afford to jump the queue and pay a private doctor to treat one of my ailments rather than be triaged on the basis of need and waiting my turn. I'd think I was doing wrong, though, if I did ... Just as I would be doing wrong if I jumped the queue in a supermarket, say, or a railway ticket office. (Less serious examples, to be sure; but the same principle: queue-jumping is wrong.)
Meanwhile, I'd like to pay more tax so as to try to diminish the length of the health-care queues. I know this is an unpopular view nowadays, but nevertheless I think it correct (in terms of what is right or ethical). It's less selfish, you see: we ought not to be selfish.