Allow me to point out a few things:
A) purchasing Chapter 1 gets you 1 update (Chapter 2 obviously).
B) Chapter 1 and Chapter 3 are the same series but really count and act as 2 separate games which happen to use the same universe and rules (with the option of not Playing the 1st 2 chapters and just answering some questions to play chapter 3).
C) $10 once every 6 months is a very cheap price (Oh no $1.66 a month) for some good new content and story.
D) Somewhere on or connected to this page is a link where you can get the free version a month or 2 later.