While I know you're pissed that he changed the price after your first convo with him, I have to admit when I first started reading your post, I was really surprised when you said they offered it for $600.
They sell frames new at 4200 for Xcut, and 6k for brilliant. According to their site, the xcut uses the same layup as the brilliant. So they basically charge their own customers, buying brand new, 1800 for the superfork upgrade. Would seem pretty odd to offer it to you for 600.
Anyway, I guess its a moot point since you are returning it.