At any rate, I don't agree that PBMs cause drug costs to increase. PBMs are simply purchasing groups for insurance companies. They take advantage of bulk purchasing and offer that service to insurers. They also handle the all the complexities in setting a formulary which includes evaluating new drugs, negotiating with drug companies and adjudicating claims. That has real value.
The best example of how PBMs have controlled drug pricing is in HCV. Express Script directly attacked the pricing of Harvoni and Sovaldi. However there was nothing they could do since they were the only HCV drugs available. However, when Viekira Pak became available, Express Script did an exclusive deal with Abbvie which caused Gilead to scramble to price match. The cost of HCV drugs came down by almost 40% overnight. It saved the health care system a lot of money.
Now, I do agree that PBMs pull a fast one on some insurance companies. They are intentionally opaque when it comes to how much you pay for their services. The smart insurance companies ask for "pass through" pricing and then pay the PBM a fee for their services. The not-so-smart insurance companies don't ask for those numbers and get put over a barrel.