MjolnirX - It seems Wal-Mart erroneously posted that the 4GB Xbox 360 Kinect Bundle had been "rolled back" to $249 (down from the standard $299). It is not a roll-back, but in fact just an error.
Wal-Mart has since released a notice stating:
We made a mistake in our advertising circular for Sunday, August 29 - Monday, September 5, 2011. On page 19, we advertised an Xbox 360 4GB Console with Kinect for $249. The price was mistakenly labeled as a rollback.
We will honor the $249 retail from Sunday, August 28 - Monday, September 5, 2011, while supplies last. We will not be able to offer rainchecks for this item.
We apologize for the error. We hate to cause you any confusion or inconvenience. We always appreciate your shopping with us and we look forward to saving you even more.Source: Joystiq
Wow, that's their own fault. At least they'll honor the mistake price for anyone who bought one.