Just as a point of clarification, I don't believe the Koetsu carts on eBay are "knockoffs". They're authentic production but coming from overseas sources they wouldn't have the US warranty, but then neither would the one for sale here since it was similarly purchased in Japan.
Well we are all certainly entitled to our opinions, and I'd prefer to not have a debate on it as this is a listing in the Trading Post area, so let's not hijack the thread.
I've had a bad experience on eBay and happen to know that given the cost of these cartridges, it's a target rich environment for fakes and YES they are on there! I never said all of them, but some definitely are and it would be in everyone's best interest to research its authenticity. So I only caution people before they dish out several thousand dollars for something that may not be authentic. I am not competing here, just merely sharing information with fellow audio fans.
You are certainly welcome to purchase one on eBay if you wish. Thanks.