The guy placing the ad JUST had this snake shed to that color less than a couple of weeks ago (if my memory serves me correctly). He posted on the kingsnake forum with pictures of it before and after the shed. Before - looked normal, after - like what you are seeing in the picture. He also got feed back that it may change back to normal.
Hey, if someone is willing to pay $1500 for it - more power to him!
Ahhh - found the link! http://forums.kingsnake.com/view.php?id=1148602,1148602