As far as I know no one actually uses them except to get the achievement. I think they are pretty rare though, so maybe people looking to collect all the pets would pay something. I'm not sure though =/
edit: I may only think they are rare because I never do the specific maps that give a chance for them to be in your shop. I don't even know what those maps are either.
This post was edited by Agreed on Nov 2 2011 01:04am