I see little point when the standard one is so good in taking a risk on wether or not an ebay purchase is a genuine item or a faulty one thats found its way from the bin to ebay.

If I was getting an aftermarket crank I would be buying it from the manufacturer directly and just accept it was dearer than taking a punt on ebay, too big a deal if it fails.

You could get it x-rayed after buying it though I guess.