Considering it cost about $2-$3 to create and ship the hardcover book to amazon, depending on amazon's cut of the kindle book, the publisher might be making more money on the hard cover.
Are you sure about this? The prices for me display as:
Hardcover, Amazon Price: $13.98
Kindle price: $12.99
The price table also shows someone selling a used "New" copy for $12.14.
Interesting, for me the Kindle price still is the most expensive: