First, there are not sufficient primary doctors for medicare recipients.

That's at least partly because primary care incomes, especially from medicare, are unattractive compared to specialist incomes. There is every reason to expect that shifting dollars across to primary care as per several of the proposals will increase primary care availability. As you note, good access to primary care costs less and is far better for patients than waiting for crisis requiring specialist care.

I'd like to get in with an observation about physician availability. ;-) All first-world nations face healthcare workforce challenges, especially as the population ages. Healthcare skills are transportable internationally and practitioners will follow the money, especially if they are disillusioned with the system at home. The US would have no difficulty attracting an army of excellent foreign physicians if it needed to; the challenge would be to lower the barriers in a fashion that is not considered racist. A good start might be to allow entry to physicians trained in one of the Royal Colleges, since their qualifications are already generally acceptable in the first world nations in Europe and Australasia. I'm saying that the "shortage of physicians" argument is a nit and that the US can get as many as it wants when the time comes, as long as the terms and conditions are attractive enough.