Amazon's Curious Book Pricing Mechanism

I have owned an Amazon Kindle for a period approaching one year now and just recently noticed a very interesting fact. I am not sure whether it is very common but it displays the extreme ingenuity of Amazon's pricing system. A couple of weeks ago, I downloaded a sample of the book, The Rational Optimist on my Kindle reading device and read through it in bits and made the decision that it was worthy of buying after all. Soon after making the purchase,  I noted that the price of the download was US$ 14.99 and therefore slightly higher that the price that was quoted on the website.

In my curiosity to find out whether there was a price hike in less than a couple of weeks, I reversed the sale  and went to check on the Amazon site. I found out that the price for the Kindle version was US$ 11.99 and bought it off the website. Now this has got me thinking about the reason for this difference in pricing for the same item. I am sure that it is not about the variable costs of the wireless service that allows for the purchase but perhaps an attempt at price discrimination. And I am more inclined towards the latter for the reason that on other occasions, I have received alerts to versions of books that are available for US$ 0.00 but upon trying to download, realized that the books now cost US$ 2.00. It appears that I managed a small arbitrage trade this time but I am unsure whether i should develop a more sophisticated model for making purchases and ensuring savings.

Image source: Amazon.com