I only found one on eBay at that price that appears, at first glance, to be a genuine Nikon grip from the pictures provided. They use the same product name and show photographs of an actual Nikon grip, but then I found this on the listing:
"Antention: * Unless described as 'Original'; all items are produced by a 3rd party manufacturer and not the original manufacturer. especially for camera Battery&Charger."
They didn't use the word 'original' anywhere in the listing.