Nick never said that they were Test Hanken but
just Test cels. The issue about Test Hanken was
brought up in the forum, but in a way they are
'test' cels for the hankens so the term is also
correct.

Anyway, the reasonament i did is still valid even
if they are not the final hankens as they are done
by the same people. 

If that is not enough take as example limited
reproductions of determined cels or other similar
art, that even being reproductions also go for
high prices (even higher than those X test cels).

Also, see that not all test cels are expensive, we
can see many of them that can be considered on a
first stage, and those are cheap, but there are
others that look exactly or almost exactly as the
final hanken, so it's normal that those are
expensive. Now think, if that test cel goes for
$500 you can be sure that the final hanken is much
more expensive.