Asus Releases Thinnest Ultrabook; Zenbook UX305 Goes On Sale For $699 : Tech : Yibada. The fact that ASUS has released the thinnest notebook computer ever isn't the news here. The fact that it only costs $699 is. If there were a computer that replaced my Sony VAIO tablet, it would be the quad core version of this guy with a better screen. Of course, that will drive the price into the thousand dollar range, and wouldn't move me to switch. If you don't already have a tablet or ultrabook, this is one to take a close look at. It is the ZEN thing to do.