I wonder if you could make this official with something like this on the home page:
"If you are interested in our product but you can't afford it, please send us an email explaining why you can't afford it and we will give you a free license".
That's it, no conditions ("at least two paragraphs, and it has to feel real!"), no lecturing, just asking people who can't spend money on the product to spend some time instead.
I wonder if the extra thoughts that would-be pirates would have to put into writing that email would be enough to make them reconsider and actually buy the product they would have otherwise pirated...