The point is not that the $8 million system did not work. The point is that it was overly expensive for what it accomplished, and it slowed down the production line significantly enough that some worker went out of his way to implement his own solution. Without his solution, product quality may still have gone up, but production numbers would have gone down since the production line would stop every time there was an empty box on the belt. In contrast, the fan not only increased product quality, but it also had no impact on number of units produced and it cost $20 to boot. Sure, it's not a perfect solution, but in this case it's "perfect enough." (And making it more perfect would still have been several orders of magnitude cheaper than the $8 million system.)