Ed:  Gem Roller Organs are _very_ common.  I see them in flea markets
for anywhere from $350-750; the higher end is for fully restored ones,
with excellent condition decals, paint, etc.  The rolls (also known as
cobs) are generally $10-20 each, and are getting hard to find.

If you'd like to have a roller organ in your collection, my
personal advice would be to spend a little more and buy a Concert
(a.k.a. Chautauqua) Roller Organ.  These play same cobs, and have same
number of notes (20), but have larger bellows, and reeds that are
voiced (so I've been told) an octave lower, giving a deeper sound.
The Concert organ case is nicer, with glass cover over the front
section.  Overall, a much nicer instrument, less primitive looking.

I see Concert organs at flea markets for between $400-900.  There
is one on eBay auction right now that comes with a number of cobs!
I started with a nice Gem, but traded it up when I came across
(and heard) a really nice Concert!

Jim Canavan