Because of the fact that the term "Non profit organization" is so commonly used, and that donations are involved within non profit organizations. I believe that any form of the word Donate, Especially in the .org extension has significant value.
You should consider targeting some end buyers, your selection is endless.
I feel that if you sell this name for less then $5,000 you would be shorting yourself. Set the price high, and see who wants it most.