That's most likely because the majority of Orphen 
cels we see in the US are not from Orphen but are 
in fact from it's uglier and much more horrible 
sequel series, Orphen Revenge, which I personally 
consider a blasphemy of animation which should be 
wiped from the Earth (the opening was decent, and 
that's about it). But I digress.

Basically, from what I understand, cels from the 
original Orphen series were never released, but 
cels from Orphen Revenge WERE. Hence, the 
majority we cels we see are going to look a bit 
like ass, as we're mostly getting Revenge cels. 
Also, since Orphen cels were never released, this 
causes their price to shoot up. Nearly any cel 
from the original Orphen will look good, since it 
had such slick and gorgeous animation. Another 
thing driving it up is that Orphen Revenge cels 
are flooding the market marked as Orphen cels, 
and people are paying ridiculous prices for 
them..when an actual Orphen cel shows up, it 
looks so much better than the rest that people 
bid like crazy. 

Basically, if it's ugly, blobby, extremely flat-
looking, and with lack of detail, it's from 
Revenge, as more often than not they are. If it's 
pretty, I can almost guarantee it's from the 
original Orphen, as I have yet to see a pretty 
Revenge cel.

-Misha