It’s worth noting that countries (such as India) have the option of simply not respecting a patent when the use is important and the fees requested are unreasonable. Also, patents aren’t international; it’s often possible to get around them by simply manufacturing and using a chemical in a different country.
Found this paper on insecticide costs: https://sci-hub.st/http://dx.doi.org/10.1046/j.1365-2915.2000.00262.x
It’s from 2000, so anything listed here would be out of patent today.
Here are the costs from the above link:
It’s worth noting that countries (such as India) have the option of simply not respecting a patent when the use is important and the fees requested are unreasonable. Also, patents aren’t international; it’s often possible to get around them by simply manufacturing and using a chemical in a different country.