The Medical Loss Ratio (MLR) requirement established by the Affordable Care Act (ACA) is 20%.
Typically it's closer to 15%.
As these are private companies, some percentage of that is obviously profit.
It doesn't cost that much more to run private insurance than Medicare.
The problem is the incentive of insurance to drive up cost to get a larger fixed cut, and the lack of a public option (which would require private insurance to actually be worth it).
The policy lever that addresses this is billing standardization, not just insurer reform. Countries like Germany and Switzerland run much lower admin under private insurance through standardized claims formats and all-payer rate setting.