I posted your pictures on TPF and the only thing that raised a red flag was the card being wrapped in plastic, but I noted that you did that yourself.
Other than that one detail though, there didn't seem to be anything else from the other pictures that was screaming "fake" as far as the other markings and the authenticity card, at least not that was noted by the girls there who seem to know their stuff more than I would.

I've heard of crazy bargains like this, even on Chanel.
I believe that one girl on TPF found an amazing pink flap at The Salvation Army, of all places. For something like $50.
It was absolutely real too, so it certainly is possible that you found a bargain.

But again, without a clear picture of the interior hologram there's no verdict being made either way, so I would try and take a picture of that using the macro setting on your camera and turning off the flash.

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Just bought another bag so I'm on a jeans ban!
Still need R&R for my little man! Size 4.