What you are saying here makes sense , but it doesn’t follow from your original point about money being made up. It seems like your point is that we need to improve on how things are valued relative to their damage. The problem with black markets is that it’s purpose is to circumvent regulation meant to factor in the cost of externalities.

The eventual owner of the rhino horn would still want the rhino horn. Your argument hinges on making someone not want the rhino horn compared to what they can get instead. So it’s more of an education and compliance problem than a money problem. The high value is just a reflection of how difficult it is to get something.

Again, your point is valid, it just doesn’t follow from your original point. Just say that instead.