The manufacturer charges a higher price to the insurer and pays for the consumers copay so they are not impacted by price sensitivity. Kind of like business travels tend to spend more because it is the companies money vs their own. If the copay is too high, consumers might shop for cheaper alternatives instead of the "latest and best".

The sticker price is negotiating leverage for use against organisations with money, the insurance companies and Medicaid and Medicare. They don’t pay the sticker price either but they come much closer because they’re price insensitive. All costs get passed on, on average to the actuarial customer.

In addition to what other commenters have said, when you write off donated units, they're worth more at that time if their price is higher.

It might be used as a starting point for negotiation with private insurers.