Comment by pas

After you file for a drug patent it takes 3-4 years to get approved. You also have to run clinical trials of various sorts, which take years, and then you need widespread marketing campaigns to ensure that doctors are aware of the new treatment. A rough rule of thumb is that it takes about 10 years from the point of filing the patent before you can actually bring the drug to market.

Drug patents are good for 20 years from the filing date, so you have about 10 years to recoup all of your costs, recoup the necessary fraction of your amortized R&D expenses on drugs that didn't go anywhere, and hopefully turn some profit, before your patent expires and generic manufacturers undercut you.

The result is that cutting edge drugs are extremely expensive for the decade or so after they first become available while the patent holder uses their patent-provided monopoly to set prices at the maximum that insurance companies and government health providers will pay. Your link is discussing the period of time after the patent expires and generic manufacturers get into the game, but the drug being discussed here with its $88,000 treatment cost is still in the patent-protected cost-recouping stage, where it's not subject to normal market principles of supply and demand because the supply side is a temporary monopoly.

dodobirdlord's explanation is solid. Basically your link describes "generic" versions of a drug (aka a "brand" drug) with an expired patent. For new drugs they don't have competition like a normal market does because of these patents. To give a summary of the section of the course I linked the market forces for "brand" drugs is the willingness for payers (insurance companies/ governments) to pay.