It's always tough receiving bad news, but nexisfan is right.
The price tag is wrong. The banding is wrong, the closure is wrong. Authenticating can be done when someone is very familiar with the dress styles, tagging associated with each season... basically the same way one authenticates designer bags, jeans, etc.
Hope you get your money back.
Oh dear... That's terrible.

http://www.ebay.com/itm/120794131084?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2648