I know theres a good chance that this is a knock-off but it has had a lot of purchases with no negative comments saying its a fake. What do you think? http://www.ebay.com/itm/2013-Razer-DeathAdder-6400dpi-4G-Optical-Gaming-Wired-USB-MouseRazer-DeathAdder-/251513369222?pt=Mice&hash=item3a8f5d7286