Just check the Who Is info (google who is ip and use one of the free sites that show up). Check who the site is registered to (the Whois info), not just the service it was registered with or the geographical location of the server.

In this case, the site is registered to someone located in China.

You get what you pay for, unless it's on clearance. I'll buy clearance jerseys from my LBS, Nashbar, or Sierra Trading Post, but I'd stay away from these and the cheap ebay knockoff jerseys.