It'd be different, I think, if the person who figured this out did it themselves, or taught apprentices to do it or what not... you really can't fault somebody for trying to learn your trick, to figure out how you do it, as that's more or less the bloody point. The problem is the danger of the trick becoming common knowledge, and therefore worthless to anyone. I mean, once you approach the point where you're selling those magic rings to folks in joke shops, you lose your audience for that trick.
Granted, charging 3 grand for the secret to the trick pretty much ensures that only serious magicians will pick this up... it'd be a lot to pay for casual curiousity. On the other hand, all it takes is one person to buy this thing and upload it to Youtube, and suddenly everyone will know how this trick is done... a trick that apparently has great personal significance for Teller, and which is the product of his genius alone.
Something HE could have sold for a lot of money, but decided not to because it was worth more to him to keep the secret.
I dunno. I have to sympathize with the guy, and I do believe that a new trick is just as much an act of creation as writing a book. However, if you write a romance novel that's a huge success, and someone analyzes your book to figure out why the emotions work and writes a different book that works for the same reasons... well, you don't get sued.
Uphill battle, indeed.