As Valerie said " I guess I'm a bit naïve, but my first thought was that this was either a factory over-run, or a factory run that was rejected by the contracting company (Jack Wolfskin)"
And I'm inclined to agree. If anybody will bother to check out the eBay listing, nowhere does it say that it's a Jack Wolfskin jacket, other than in logo in the picture. It's simply advertised as a wind jacket.
As many have mentioned, the logo is on the "wrong" side. This could have been the factories mistake, and the jackets they produced could have been rejected/canceled by Jack Wolfskin and they are selling it to make up the loss, while not explicitly advertising it as a Jack Wolfskin jacket.
Of course, they could be counterfeit as well, the point is, none of us know. But, at the price and the fact that they aren't trying to exploit the brand name in the listing makes it seem more likely that it's a overrun/canceled/mistake production.