The scanned image shows the premium Xbox 360 with a 20GB HDD for $299.  This would be a $50 price cut to that model effective July 6th.  If this turns out to be the actual price cut it will bring the Xbox 360's price to the launch price of the original Xbox.  This price cut also implies that the Arcade model will most likely drop to $249, the same price of the Nintendo Wii. 

It's not too outrageous to think that the premium model will drop to $299 since a price cut will come around E3.  Last year the 360 dropped $50 before E3 on the premium model.  This move will help the 360's sales improve from this price cut and if Sony doesn't respond with their own price cut then we should see the end of the PS3 outselling the 360 in North America. 

Source:
joystiq.com -rumor-xbox-360-dropping-to-299