Gamasutra has posted an article of mine called "Beyond Scrum: Lean and Kanban for Game Developers". The article culminates what has been described here about using lean practices since 2006 and applied to games in production and details how Scrum teams can adopt Lean practices.
If you want to read more about Lean and reducing production costs by more than half:
Lean Production, first steps, September 2006
Google Talk with Mary Poppendieck, December 2006
Prototypes, April 2007
Book review: Implementing Lean Software Development, September 2007
Cooper product design applied to game development, parts one and two, August 2008
Phases in an agile game project, September 2008