If you think that the Xbox One controller took at least a month to make, you are incorrect! It actually took two and a half years! Why $100 million? Not all of the money was put on specifically the controller. Hundreds of prototypes were made, thousands of hours of user research studies, and creating new tooling and construction facilities! An insider's look of the controller was posted by sc_shark and looked pretty similar, but most of the changes were internal. The feel of it changed, Dpad changed, keys were minimized by a little, and a lot more! Was the money really worth the improvement of the controller?
Via CVG
Building a games pad is, one imagines, similar to constructing a grand piano; just a single malfunctioned key can undermine the entire design. This was why there was an inherent danger to Alam's plan - he wanted to take a forensic look at many of the Xbox 360 controller's constituent parts and see if they could be enhanced without compromising the overall quality.
Via CVG