I infer that this was a first-visit outcall for this gentleman for you. I note you left out if there was any confirmation of the session's donation when making the arrangements.
Kelly, was there any discussion of the donation for the time requested when arranging the session? I'm making the assumption that there wasn't in my response. Of course, I understand not discussing the donation during the session.
So I'm going to illustrate how I would conclude $250 was expected if not discussed.
I note that you list a $50/hr P411 discount. Your ECCIE showcase lists your outcall donation as $300/hr. $300 - $50 = $250. Since you mention his P411 OK's, he probably booked this way.
I always discuss the time/donation in the communications to book a session. I've never had that be met with any hostility. I suppose I usually bring it up, but not always - sometimes the provider confirms her rate for the session's length of time.
I would hope the other providers don't view this as such an affront by Shaft. Unless other providers report that the same hobbyist shorts them too, give the guy the benefit of the doubt: he left $250 instead of $300, and it was probably an honest mistake.