If it seems too good to be true, it probably is. I always check the seller ratings, feedback, and if he made any accounts besides that one to see if the seller is reputable and legitimate. And like Alex Chin said, if it's not made in America, it's not genuine, unless the product originated in a particular country or it was intentionally outsourced by the company.
If you're ever thinking about getting into the retail business, make sure you buy the right wholesale goods from the right people. There are many wholesalers based in China that sell counterfeit merchandise, especially electronics. The only legitimate products that you can buy are generic goods, not name brand crap.
I've seen quite a few ebay sellers unknowingly buy fake merchandise, sell it, receive many emails from very angry customers, and have their account shut down for selling counterfeit goods. The Federal Trade Commission won't repay you back for the money lost, and the Immigration and Customs Enforcement will come knocking at your door if you import enough fake goods from China. Take everything with a grain of salt and be smart, that's all.