actually, doctors wages aren't the problem in hospital pricing. In fact I think they deserve more than they get on average. Administrators could use a pay cut though. The real problem is a price fixing system they call the Chargemaster. We don't have to mandate prices, we just have to remove their ability to price fix. No one wants to cripple hospitals financially, we do need them, we just need them to base their prices on the actual cost of care. Capping a doctors salary, wouldn't affect any price. Because the prices aren't based on cost. You could triple every doctors salary in any given hospital, wouldn't affect the price. The hospital could more than afford it, despite the public image of a struggling non profit that most hospitals try for. They rake in more than oil.
I wouldn't recommend integrating single payer, til the price fixing problem is resolved. Last thing the government needs atm is to be put on the hook for chargemaster prices for the whole country. Even then, going to single payer raises a whole slew of other problems. Insurance Companies turn a profit off interest generated from collected premiums. They build a pool of people, say for example 80 healthy people and 20 sick people. While they are paying out for the sick people, they are adding the premiums of the healthy people to their general investment portfolio. Which for a company like United Healthcare is worth a few billion. They then invest that money in things like energy, municipalities, and bonds. A great many local economies are funded through insurance investments. Killing the insurance industry could send us into a full blown depression. That is a real risk, its why Obama backed off the public option.