Long before the existence of IP, people who developed something new would keep their manufacturing process secret in order to prevent competition. Even today, sometimes they still do (in fact, the purpose of patents is to discourage trade secrets).

Now suppose someone invents a new medicine, or a new alloy, or a new machine, or a new algorithm, and refuses to tell anyone how it was made or how it works.

And suppose reverse engineering isn't feasible. Maybe it's too much work considering the value of the product (nobody is interested in reverse engineering your particular favorite shampoo). Or maybe the machine uses sufficiently strong encryption to prevent its reproduction. Or maybe there is some other obstacle.

Again, before modern capitalism these problems were the norm. If you wanted a very particular product, you often had no choice but to find a very particular provider.

As before, at what point does paying someone to help make such a product become exploitation?