Born Again At The Laundromat

There is a cart of books in the office hallway at the local Denver bookstore where I work, and it has been sitting there for about two months now.  Each time I walk past it, I glance at the titles, which all seem to have a western theme, and one -  a used copy of Born Again at the Laundromat, by Dave Carty - grabbed my attention, and I bought it.  It cost me $5.00 plus tax, and I was shocked to find that I didn't get my employee discount because it was considered a "collectible."  And I am not sure why.  Carty is a freelance writer, mainly for outdoor magazines like Field and Stream, and this was his first (and as far as I can tell) only book, a collection of non-fiction pieces about the "New West" and published in 1992.  Carty went to school at Colorado State University up in Fort Collins, and lived in Boulder for half a dozen years before moving to Montana, where he still lives.  I googled him, and he has his own web site, where he offers his skills as a freelance writer.  But once again I ask - why is the book considered a collectible?  It is a pleasant enough read, and mildly interesting, but I suspect somebody at the bookstore is a friend, and put the fix in, resulting in me losing my $1.75 discount.  Perhaps I should e-mail Carty and demand he send me a check for that amount. Plus tax!