You missed your own point about copyright and 
printer...

However, 
I know lots of collectors who dislike fancels. 
They are perfectly entitled to their opinion 
Some collectors who'd spit on a cel without its 
matching douga/genga/Sketch or was not a key cel.

Because face it - if your going to be elitist - 
Unless a cel has been done by the key animator - 
its probably been filled in my some smelly 
learning in betweener and painted out by some 
subcontracted studio in Korea/China and if China 
probably by in some prison camp 
(Prisoner 2516, you have not met your quota of 
painted cels today - you get no food).

But seriously do you THINK about these things?
Do you ensure or try to buy only cels numbered 
(1) or (End)? I know I'm not that picky.

Yep those madhouse test cels never saw the light 
of book/video etc. They were based off drawings 
not by Key animators but original drawings off 
the Character Designer - Yuki. So not some mangy 
other person.  They were probably painted in-
house to test for colour ie by Studio Staff. So 
whilst not production art in the purest sense I 
am happy to have them as they are probably closer 
to Yuki's original thoughts.

Would you prefer a cel from Mononoke or a hand 
sketch from Miyazaki? 
Perhaps you and I would ascribe different values 
to such items but take care when you stand on a 
elitist soapbox