Overpriced Copy of Sign of the Four

There is a copy of Sign of the Four in Gregg Shorthand listed for 463.00 USD on Amazon.  Does anyone have a clue where someone comes up with a price like this? 

This book is as common as dirt.  There is only one hardback PA 1902 version from late 1915, and the binding is very strong.  Many copies have survived.  They kept printing and selling this book from 1915 through the 1940's.  Copies are available from several online book sellers for 10 to 20 bucks. 

This makes no sense to me.

(by Paul for group greggshorthand)