This appears to be ahead of the new Xbox One S launch on 2 August, so Microsoft is probably just trying to empty its warehouse of 500GB versions of the Xbox One. This includes bundles with games like Gears of War: Ultimate Edition, Quantum Break, Forza Motorsport 6, Rise of the Tomb Raider, and Rare Replay.
Retailers like Best Buy and Amazon will be selling Microsoft's Xbox One console at the new price and Redmond says that the price will only be "while stocks last". It is not clear exactly how many Xbox Ones have been sold as Microsoft hasn't provided sales figures for ages. EA mentioned that Microsoft had sold 19 million Xbox One consoles back in January.
Microsoft's updated console is 40 percent smaller, and the redesigned hardware has been widely praised. With a new Xbox "Scorpio" console due next year, it's hard to imagine that Microsoft will continue manufacturing the original Xbox One hardware once stocks have cleared