Per, I agree and disagree at the same time.

I'm retired. I set out to develop a method to make and coat silver halide emulsions for B&W paper and film on my own. I have ended up being invited to give 2 workshops using this material.

It has cost me several thousand dollars and over 2 years of my time to do this. I will never in the rest of my life be able to recoup the costs of development even with paying workshops.

And, if even one student begins teaching a free workshop using my material that I taught them, it undercuts my ability to continue financing further work. OTOH, they have a perfect right to do that if they wish, I suppose. But, they cannot use any of my copyright material.

So, I'm in that dilemma of both agreeing and disagreeing in free workshops. See my answer to Donald Qualls in another thread. I'm doing the best I can, but sometimes free just does not work. Someone eventually must pay for the expertise and experience of another. It cannot just be handed over sometimes. So, there is no simple answer, although I wish that there was.