I purchased these two shells at a yard sale for $4 each.  I thought they would look nice in my daughter's ocean-theme bathroom.  After looking them up on the internet, however, I'm wondering if I should risk placing them in a 3 year old's bathroom.  Are these Turbo Marmoratus shells, and are they selling for approx $70 each for 5 inch shells?  

http://stone-pathway.com/images/Others/shells-0002.JPG

Yes, these are "pearled" Turbo marmoratus, which means the outer layer of the shell has been ground away to reveal the underlying natural pearl layer, and the shell has then been polished to create a decorative item. The top photo on this page shows what the natural shell looks like:

http://indopac.tripod.com/turbans.htm

I have seen large specimen quality shells - that would mean natural condition with the operculum present - for prices similar to that which you mentioned. I have also seen some offered for about half that. I don't know what a gift shop would ask for a pearled specimen.

Thanks for your help - Dene