It’s very simple. In the US your pharmacy has a contract with the drug supplier that prevents the pharmacist from telling you that you could buy the drug without insurance for $10 while he charges you the $20 copay. As long as this is legal and your pharmacist’s duty isn’t to you the patient, don’t waste time worrying about the details.
I am grateful to every pharmacist / pharmacist assistent who's sotto voce ignored that immoral "rule".
On the flip side, before I transferred my prescriptions to my (excellent) locally-owned small pharmacy, I checked that these are drugs on which the respective Pharmacy Benefits Manager allows them to make a profit rather than a loss. That reminds me that I'll need to repeat that conversation when our insurance changes in January.
