I agree... If they're selling the tutorial, then make and sell to your heart's content!
The classes I teach, I'm showing students how to do specific designs, etc. and they are welcome to do what they will with them. Selling a tutorial is the same thing, only the instructor is "in the pages" not in the classroom.
If someone doesn't want anyone making their designs, then don't teach people how it's done! As others have said, anyone saying that to you is full of BS.
Now, how did Chihuly do that one?
Jim