Cost: Kindle Edition vs. Hardcover

Can someone please explain to me why the Kindle edition is more expensive for Seth Godin‘s book Tribes?  The hardcover is $13.57 but the Kindle edition is $16.99.   I love my Kindle, but I was of the mind that electronic version of paper books would be cheaper in every circumstance.  Obviously I was wrong.

Do you know of any other books where this is the case?