Speaking from an ex-director of a non-profit point of view, with a sociologist's bent ... some (not all) non-profits operate in paradigms of woe-is-me. There can be prevailing notions of "great need" and despair and a certain sense that "the world owes it to us".
For such organizations, there will be a strong mode of asking, asking, asking--for discounts and special gifts and so on. It's part of their prevailing belief systems. And from these you can anticipate "pushing" for deals, etc. And they really expect that they deserve it, just because they are non-profit and have an Important Mission.
So there's that.
On the other hand, all non-profits like to save money. So, it's not unusual that they'd ask. But there's the framework of "entitlement" and there's the framework of, "do you have any discounts or gifts for non-profits? We're not expecting, we're just asking."
And that's where you chime in with the response that corresponds to your personal or company donation policy, whatever that might be, e.g. "I give only to only to organizations whose mission is xyz" or, "I have already donated as much as my budget allows this quarter" or, "Sure, I can give you a $___ donation of my services."
This topic has come up a few times on Biz Talk with, I think, many rich comments. A search in Biz Talk for "donate" will bring up some of them.

