You make a valid point, and I'm interested in 
what other people have to say.

For my own answer, I would say that they are 
unique and rare production art items in general. 
And if you are referring to "X" test cels, well, 
then I have to mention that these cels normally 
sell for a lot of money (i.e. $500). I agree 
there is no way to authenticate them... but I'm 
fairly confident that they are real. (established 
dealer etc.)

~Tara