@Crussel - see all my previous comments on "accuracy" - that the Adobe algorithm comes out at about twice the paperback size sounds "correct" from my own comparisons.
As to why ithe APNX calculation for a MOBI file would come out at 2 pages, my guess is that the book internally does not use <p> tags for paragraphs. Take a look at its content to confirm that is the case. If it is the MOBI format that it is counting the pages for then the issue lies with the APNX calculation code written by user_none, you could try posting on either the Kindle page count thread in the Devices forum or on his APNX plugin thread. He is aware that his calculation does not for instance consider <div> based paragraphs that some books use instead of <p> based ones.