Yes, I know the drug manufacturer gets money from sources other than US insurers, I never said otherwise. But we're talking about the US system specifically. Money from premiums to insurer, insurer pays PBM, PBM pays drug company, drug company gives back discount/rebate. Sure that $700 they are handing back could be money from some guy in France but it doesn't matter. The PBM could just pay $300 to the drug company and do what they want with the $700, it's effectively the same thing.
No, this isn't how the transaction works. You're imagining an exact transfer of costs, from the member of the public onwards. That's not how insurance functions, and this entirely omits how premiums are
determined.
* Insurer sets premium, according to the likely costs to itself + desired margin. If they envisage Drug A will ultimately cost them $400 if required, they set monthly premium at $100, say.
* Hundreds of millions of people pay $100pm.
* The insurer requests the PBM source the drug. Gives them $1000 per prescription, knowing the ultimate cost will be ~$400.
* PBM pays $1000. $800 comes back as rebate.
* $600 is sent onto insurer. PBM pockets $200.
So: the premium is set according to the ultimate projected cost to the insurer. Which doesn't include the rebate pocketed by the PBM, which was never with the insurer or the individual insured.