Effect of Educational and NGO discounts?

I have seen many websites, especially SaaS, offering discounts for students and NGOs.
Besides the obvious fact that you are helping other people and no doubt that's great, I am wondering how does this impact in the general profits/revenue of the product. I guess a (usually) 25% discount maybe cuts a little bit the margin but increasing the exposure to your product can also attract other customers not eligible for the discount.

Does anyone have experience or do you know of any companies that wrote about this? Thank you!