Its a toss up. I just bought a few genuine Spyder shirts from a store here in NY called Century 21, (you may have seen it during 9/11, it was one of the stores accross the street from the towers). At any rate, I got the shirts for more than 50% off.
Now as far as buying stuff from over seas obviously the risks are augmented, but that still does not mean that its not genuine or as good as the real deal. I have a friend that manufacturers clothing, one of his lines is called NorthSportif, he goes to China tells them what he wants they make and or draw out a few designs, he approves them and they get made IN THE EXACT SAME PLANT THAT RALPH LAUREN makes his stuff, using the same materials. This isnt exclusive to jackets most high quality metal glasses frames are made by 2 companies in Italy regardless of the brand.
PS: a tip about buying designer name brand items on ebay. When an item is listed as authentic, that only means that it is true to the original, not that it is original. Genuine on the other hand means nothing less than that it is made and designed by the original maker. You will find few people that are willing to say that their designer products sold on ebay for 1/5 the retail price is genuine.