I’ll speak on one from personal experience. I have been on a med most of the last 20 or so years for a chronic illness. I believe the drug hit the market in 1997 and as of 2018 was still making the company 1.7 billion dollars a year. That 1.7 was actually 44% lower than in 2017. Looking briefly now it is finally taking in less than 1 billion a year, but still 800 million. It isn’t dropping in revenue because they lowered the price. It is because other meds have been introduced so they have a lot more competition.
There was even an event where press asked the CEO about having made back their development costs and then some, which he agreed they had, would they then lower the price? He said there was no reason to lower the price as it was a huge revenue source for them.
Over 20 years later the costs for it continued to climb rather than lower. Costs for it estimated at 10k per patient in 1997 and around 70k now per year.