If physicians were the primary driver behind high healthcare costs, I would expect physician income to be a larger fraction of healthcare expenditure. Currently, physician pay represents about ~10% of US healthcare spending. This is dwarfed by administrative costs, which represent 25% of US healthcare spending.

If the AMA/AAMC are to blame, then it seems likely to be implicitly: by keeping entrepreneurs out of the hospital administration game so they can't reduce inefficiency. But you don't have to be a physician to be a hospital administrator, so this doesn't make sense to me.

Reducing physician salaries to 0 only reduces healthcare costs by <10%, and entrepreneurs can become hospital administrators without becoming physicians. So, I think that the ire directed at the AMA is misplaced, but I'd be interested to hear more (and I'm an obviously interested party, though I'm not an AMA member). The regulatory bodies are most likely what you have concerns about.