I know nothing about the topic, but I do know that insulin is a naturally occurring molecule but it wasn't a slam dunk. For years it was extracted from pig and cow pancreases collected from slaughterhouses and fed into a blender, but it required a lot of development to filter out the non-insulin molecules. In fact, some people would eventually develop allergies to their animal-derived insulin due to the trace amounts of other proteins that would slip through.
One of the first targets of genetic engineering in the mid 70s was putting a human insulin gene into e coli (I think yeast was tried too). But it isn't that easy -- the e coli genome needed other changes to prevent the e coli from degrading the molecule, as it was a waste product as far as the e coli was concerned. It took until 82 or so before that was viable.
But that isn't the end of it. The insulin generated is not active -- it needs to be cleaved from the "cluster" that the generated molecule into individual active insulin proteins. That naturally takes a few hours, which isn't great for diabetics because they need to anticipate their need hours ahead and if they overshoot they can go into a coma, and if they undershoot it takes hours to correct it.
It took years to design "fast insulin" which can be absorbed in under half an hour.
I know all this only because the most recent "Daniel and Kelly's Extraordinary Universe" episode:
It’s not hard to start a venemous snake farm. Most states allow venemous snake keeping with various levels of oversight (some states there is no oversight) I think it has more to do with how hard it is to get venom out of a reclusive rear fanged snake.
The main point is just that “naturally occurring” has nothing to do with price.
