That ad you saw for a €349.99 Xbox One? It was posted in error, Microsoft says
Console gamers had reason to be excited when an online ad depicted the Xbox One getting a price cut to €349.99, which hinted at a global price cut. Unfortunately, that excitement was short lived. Microsoft threw a wet blanket on the rumor and confirmed with our sister site, Tech Radar , that the Xbox One listing with a reduced price was made "in error" and that it doesn't have any current plans to lower the price.
Microsoft already lowered the price of the Xbox One this year by removing the Kinect motion control sensor as a mandatory part of the package. In doing so, Microsoft has been able to offer the standalone console for $399 instead of $499, putting it on par with Sony's PlayStation 4.
There have also been rumors that Microsoft will release some Xbox One bundles in the near future, including one on August 26th that will package Madden NFL 25 with the $399 Xbox One.