I apologize for the confusion. Lizzy's essentially right. I have cautioned people about this on my Amazon Connect page but I don't think anyone reads it.
Other than some slight formatting difference, the two books are identical. The dates mean nothing. Both editions were updated a couple of weeks ago within minutes of each other.
Amazon picked up the Mobipocket version, listed it and set the price at $9.99. The price I set for the Kindle version was $3.99. I’ve contacted Amazon several times about the issue and they always apologize and tell me that it will be removed but it never has been. The last time was a few days ago.
The formatting differences make the $9.99 version a few pages smaller because extra linefeeds are ignored by Mobipocket. Trying to use Kindle locations to find typos between the two versions has proven to be problematic.