There are many ways to do pricing and I won't pretend that my method was scientific. Lowering the price of the book may (or may not) have increased revenue. I priced the book this way because I felt it was fair value for the content.

These two articles on pricing nicely highlight some reasoning behind low vs. high: http://blog.asmartbear.com/perfect-pricing.html and http://blog.asmartbear.com/higher-pricing.html.