The Xbox One is currently on sale for $399 before tax, $100 off its regular price, at Amazon using code XIAMAZON.
The Amazon sale consists of the console, which is listed on the website for $449, and a free digital copy of Forza Motorsport 5. The $50 discount will be applied once the product is added to the cart and the code is entered at checkout.
The Xbox One recently went on sale for $449 at Walmart and Best Buy for an undisclosed and limited period of time. According to Microsoft, the $50 discount on the Xbox One at Walmart and Best Buy wasn't indicative of a price cut from Microsoft, saying "it sets a suggested retail price, but specific pricing and offers vary by retailer."
We've reached out to Amazon to ask how long the deal will run for.
Update: The deal is over.