This is not to say that doctor's pay shouldn't be addressed, but the system doesn't get reformed because every discussion on fixing it gets derailed into a discussion of doctor's pay, which is literally the highest-effort lowest-payoff part of the problem. And the situation stays bad because of this dynamic.
Not on it's own, but doctor shortage can still contribute to medical costs.
Do doctors make more mistakes due to high patient loads?
Are preventable items missed because doctors can't spend enough time with patients?
Would people be less likely to abuse the ER and/or wait to address conditions if they could get a primary care appointment more easily?
If doctors had a little more slack in their schedules, might they innovate in other ways?
If we had more doctors, would it be harder for mega-hospital chains to gobble up the supply of doctors in your area, leaving more independent practices to innovate in other ways?
What if your pharmacist could do most of the practical things that matter to you about your medication, rather than requiring prescriber permission?
What if you could do X by going to a psychologist or optometrist, or some other profession that doesn't currently exist, instead of going to an MD or PA or LPN?
What if you could just buy certain things directly without a middleman?
US healthcare is over regulated in general (in many areas, even as it's arguably underregulated in others).
Right now US healthcare is very hierarchical, with physicians at the top, nurses close by. Other professions and services are subsidiary to them. You don't get to choose a provider based on skillset per se, you are forced to abide by this hierarchy.
That's the real economic cost, the restrictions in provider and service choice.