Not so long ago, you could almost distinguish the real from the fake on EBay just by the price. But the scammers today are putting $1000-plus BINs on fakes!
There was a mustard "city" up a few weeks ago. The leather looked so good, I got excited and sent a question to the seller. Then I took another look and saw that the bales, tag, etc. were all wrong, so I sent a "never mind, I just realized your bag is not authentic" message. Seller responded, "Suit yourself. It's real and I bought it at NM."
Two weeks later, I got an e-mail from the seller saying I must be mistaken, because the bag is real and I must not understand how the tags are marked. I responded with photos of her bales and tags next to photos of real bales and tags. Never heard from her again.
But I can see how a casual buyer could be totally fooled.