It’s a common mistake to misunderstand the gray market and the fake / replica, Gray market are selling authentic watches, but aren’t sold by authorized dealer. With the popularity of internet, a lot of store when with online shopping, offering product that they might not be authorized to sell online, if at all.
The main drawback in buying from the Gray market is the loss of factory warranty. This might be a concern to some people, but often the price might be worth the possible trouble.
eBay and online auction site are usually full of gray market seller that sells brand news watch, that are genuine and come with everything. Sometime, they even offer their own warranty to overcome the loss of the one from the factory.