My wife has had Aetna medical insurance for several years. I gathered Aetna profit figures, number of shares, overhead (Selling, General, Administrative, number of insureds they have. I divided the overhead by 2 - if you don't aggressively sell, let's say, like with a public option, your expenses go down. Probably I should divide by 6. Anyway, my wife's payment - discounting her employer's payment, consisted of about 7% in profit to Aetna and in paying the heavy overhead burden of Aetna (for Aetna).
This needs to be an academic study with much more time spent gathering and refining data. Still, what it says to me is that the US could easily drop it's medical care expenses by 10% just by having a public option. Without thinking.
Of course perhaps a number of insurance companies have to go out of business. People will be out of work. Senators will not get kickbacks.
As said in the previous post, the days of health insurance are numbered. Maybe we make progress in the next 20 years... Sigh. At some point people will figure out that there is no real need for or value added from health insurance companies.