In sketch packs that I've obtained, often the
layout sketch (or at least one of them) is a
photocopy.  I usually get an original layout
sketch with a cel that comes with a matching
production background.  So I assume that after the
art director makes the layouts, the original
usually went to the team that paints the
background, and the photocopy went to the team
that sketches the gengas.  

Also, I know that there are doujinshi that are
constructed from photocopies of gengas (I have one
for a scene from CCS).  Don't know the origin of
these: maybe someone lucky enough to get a whole
series of cuts direct from the studio.  Anyhow,
someone involved in constructing one of these
might have extra photocopies of sketches.

For my collector's nickel, this is similar to
settei and storyboard packs.  Yes, you can buy
them, and they are interesting to consult.  But if
I'm going to spend money on an auction, I would
like to buy a unique art work, not something that
potentially hundreds of other people also own.