When there is a claim that there exists an arbitrage opportunity worth billions of dollars, I would consider it common sense to consider why has no one claimed the arbitrage opportunity yet.
The world has many very smart people spending many hours working very hard to find these opportunities, so the likelihood of it just sitting there like a $20 bill on the street, and not being picked up, seems quite small.
I do not know the answer myself, so I am interested in finding out. reddicky posted this:
https://www.hopkinsmedicine.org/news/media/releases/why_peop...
which sort of answers it:
>Biotech insulin is now the standard in the U.S., the authors say. Patents on the first synthetic insulin expired in 2014, but these newer forms are harder to copy, so the unpatented versions will go through a lengthy Food and Drug Administration approval process and cost more to make. When these insulins come on the market, they may cost just 20 to 40 percent less than the patented versions, Riggs and Greene write.
So it looks like there is some expensive expertise involved and investment into R&D that needs to be done.