According TFA, ACE inhibitors, a very useful, very common and now very inexpensive medication came from the venom of the Brazilian somethingorother viper. Yes, it went through the period of time when it wasn't generic but once the general active structure was worked out, there was a time when there was the ACE inhibitor of the week club. The dozen or so competing drugs kept the prices sort of reasonable.
So yeah, Big Pharma gets it's cut, but for small molecules (as opposed to biologics which are antibodies which are much harder to manufacture*), once the structure gets out, it's pretty much all over for the original company. The point being that venoms are biologically interesting molecules. Nature has manufactured structures that do neat things to other cells (blow them up, gum up the power plant and a host of other mechanisms). Once we know the structure, we can tweak it. Protein chemistry has come to a point where determining the structure of a complex molecule is basically a PhD thesis. Then you can work on smaller molecules (easier to make) that can modulate the original enzyme. So a whole new class of venoms is a big deal.
* biologicals are now being manufactured by the generics (isn't progress wonderful). Big Pharma is fighting back by trying to get those manufacturers to go through the clinical trials showing safety and utility - a huge time and expense. The problem (from a libertarian point of view) is that Big Pharma has a couple of good points. Biologics aren't the 'same' molecule - they're close. But until we have a lot more experience with them, it is not unreasonable to do the clinical trials. The generic manufacturers, of course, have a different view.