This isn't common knowledge. If I were to go about town and ask 100 people this question, I know the answer i'd get from all of them is "I have no idea what you're talking about." Do you know if he has an XDK or not? Seeing how XDKs are only 1000 dollars or so, they aren't all that expensive, meaning anyone could purchase one if they wanted to. So I suppose, he can stop being sarcastic and you can stop assuming and saying what you think is common knowledge.