It is not easy to identify whether the item genuine or not. I've made several purchase that I thought it was a good deal but actually it was rubbish.
by the time, I try to improve my method to identify the real condition of the item.
First, don't trust the picture they gave to you. Most of the time, they just grab it from the official website.
second, ask the seller, whether it is genuine or not. If the seller didn't reply you, the deals look so interesting and the timeline is getting closer.... well, forget about it. even for 5 dollars stuff and the seller offer return policy, I really suggest you to leave it (mostly, you will not return it at all, because it is so cheap... right?)
It is better to have detail communication previously than to have brand new "trash" in your house.