just remember the old saying. "if its too good to be true, it probably is"
edit: even newegg accidentally sold fake i7's
Newegg sold fake i7s? Oh jeez, that makes me wonder.
Anyway a 980x at that price is unreal. Ask the guy why it's so cheap and ask him if you can refund it if you don't like it. If he says no, ask him why. If he's hesitant, it's probably fake dude.
Are you getting a 2600K from the same guy? The 2600K at 200 euros is pretty good and that isn't as scary as the 980x price. But it might also be fake since he's selling it for such a cheap price.
Your safest bet is to wait for a 3570K and buy that instead.