Short answer: Because they can.
Amazon's prices are in the same range. Read somewhere that Amazon (and perhaps others) utilize an algorithm that surveys prices and if it runs across a high price, it bumps up their listed book to the same range, but one slightly higher and the other slightly lower. It is an artificial, inflated price unrelated to actual sales. It is a dog chasing its tail.

http://www.cnn.com/2011/TECH/web/04/25/amazon.price.algorithm/index.html Gil