Novo Nordisk's profits have seen a similar rise.
Now, im no economitician, but I'd wager a vial of Fiasp® that there's more than just supply and demand going on here.
> Novo Nordisk also published data for two of their insulin products, NovoLog and NovoLog FlexPen. Since the early 2000s, the CAGRs for the list prices for NovoLog and NovoLog FlexPen (Fig. 7) have been in the range of 9.8–9.9% (22). This translated into large total increases in the list prices: 353% (2001–2016) for a NovoLog vial and 270% (2003–2016) for a FlexPen. In contrast, net prices received by the manufacturer increased at a more modest rate (3–36%) with CAGRs of 0.2–2.1%. Novo Nordisk, Eli Lilly, and Sanofi have reported that rebates have grown rapidly in recent years, representing more than 40% of U.S. gross sales in some cases
[0] - http://care.diabetesjournals.org/content/diacare/41/6/1299.f...
A lot has changed in the last 20 years. A lot of regulatory and insurance law changes. When the law mandates that we pay for all our medicine via 3rd party intermediaries, you can expect a corresponding price increase as those 3rd parties add their intermediary markup.