Our cost is annual per user. I'm not sure what their base rate is, I know we're receiving special pricing because we were a very early adopter. They may very well give you a discount if you mentioned that we referred you and that you're a charity. They're good people.
As for justification, it made perfect sense for us to use something like Jostle. We have over 250 staff in 10 nations, and we were pretty desperate for something to help us keep connected, keep relationship strong, share testimonies of what's happening in our churches, etc. We love it. Happy to chat on the phone or via email if you want to go deeper.