Actually, there is lots of fake racket in the market. And, sometimes, the fake products is so real, until really hard to spot. A good way to avoid is get from reputable seller. Anyway, since you intend to get yonex, as a guide, you can go to their website, they have a page to teach people how to spot a fake yonex.
Off topic bit, sometimes, I wonder what is the real of the racket production cost

. Reason, those branded, high end rackets, like yonex, li-ning, victors really expensive. Ok, they claimed that these rackets have the latest technology, etc, etc. Then, you can also get "similar" racket, such as Apacs, Fleets, etc at even 1/3 of the price. And, these brands, I would say in the market for quite sometimes, they even claim that they have same technology, eg nanoscience, slim shaft, etc for their racket too. So, I guess these new technolgy is not propriety to the high end branded racket, but available to all, if not, sure, yonex, etc will sue them. In fact, when I was even told, these "second tier" brand of clone racket to the high end racket is about 70% to 80% in term of quality and feel of the top end racket they cloned. But, disclaimer, I personally not so lucky got chance to try out these real high end racket myself, so, I could not vouched for the statement by those racket seller.
Therefore, from the above view, I would say that the reason why these branded racket so expensive is that we just paying for their brand, for their new technolgy (of which none propriety) and sponsorship to those world players, not because the production cost.
What you all think?