I have never seen an original storyboard on 
Mandarake, they have all been photocopies.  
Normally the animation director or character 
designer will hand draw a storyboard for the 
opening, ending, and the episodes.  This 
original will then be photocopied and given to 
the key animators.  The character designer 
usually draws the setteis also and there is only 
one original for each sheet.  The originals are 
then photocopied and distributed.  The original 
ones that are photocopied usually have a binding 
to hold them together.  The original settei also 
are drawn on larger sheets of paper than 
douga/genga that you get with cels.
   I think that an original settei (one sheet)  
depending on the series can go for $350 to 
$750.  Original storyboards, if you can find 
them, can vary from $500 to $1000 per board.  
    You can definitely tell the difference 
between an original settei & storyboard and a 
photocopy of it.  The work is beautiful on the 
originals and done in pencil.

Hope this helps,
Linda