How many "Cash" buyers are there? This entire market is driven by insurance companies, Medicare, Medicaid, and a few companies who offer discount pricing. (GoodRX?? ... I am not sure how they work, but my pharmacy routed a couple of my orders through them when I went into the Coverage Gap; they were even cheaper than Medicare.)
Everyone seems to be playing angles in this business ... Even buying generic is strictly speaking companies offering inferior quality drugs at a much lower price ... and then claiming the the quality is the same.
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Also, note that often times your copay at the pharmacy is higher than the cash and carry price for the same thing.