Do not get anything from eBay for less then what the big name stores and brick and motar business sell them for. My friend bought some on eBay for $90 compared to my real one's and from a distance it seems to good to be true because it is. The fakes are a nice try, the tips are crap, the weight in the earpiece is half of the real thing, and the cable is of less quality and stiffness. Unless the seller can guarantee and provide proof that they were originally purchased from a credible seller, save your self the trouble, grief, and smacking yourself on the forehead.
I think most of the fakes are well known by the sellers, and they play stupid when asked questions on authenticity and down right lie. Many years ago, say ten, things on eBay were a good deal and most likely the real deal. Now, a lot has gone to hell and back. Ebay pretty much controls the whole auction and payment process since acquiring PayPal.