Following the $499 price announcement for the Xbox One at E3, Sony's announcement of a $399 price instantly surprised everyone watching. If you analyze the $100 price difference, you can easily understand how the Kinect and hardware for cable television capabilities drove up the retail price. According to multiple sources, IGN claims that a few months before E3, Sony decided to drop the PlayStation camera they initially planned to include in every box.
When Sony decided to remove the PlayStation camera, they informed retailers of the camera's removal, but not the lowered price. The camera's exclusion introduced a number of advantages but also introduced a number of new disadvantages. Presenting a $100 cheaper console over the competitor will drastically factor into the purchasing decisions at launch. But unlike Sony, Microsoft decided to force the Kinect into every console to ensure that developers could find no reason to not include Kinect functionality when releasing an Xbox One game.
For Sony, the exclusion of the camera puts them in a position where camera functions depends on how many people decide to purchase the $59 accessory separately. Without the camera, this makes the LED lights built into the controller a wasted piece of technology unless majority of PS4 owners purchase the camera.
At this moment, Sony's decision to not include a camera seems advantageous as the company raised internal sales estimates following E3. But until the PS4 exists for a few years on the market, we cannot predict if the exclusion of the camera will ultimately hinder the console's growth or change nothing at all.
Source: IGN