Hello Paul,

I assume you mean the "paper nautilus", Argonauta argo.  Retail price on
these depends heavily on the size, more so than for most other kinds of
shells.  Approximate values might run something like this -
3-4"  $10.00
4-5"  $25.00
5-6"  $50.00
6-8"  $75.00-$100.00
8-10" $150.00-$175.00
These values aren't carved in stone, but they will give you some idea hopefully.

Regards,
Paul M.