I don't think it would be terribly difficult to forge grain on plastic, so we can expect to see better quality plastic replicas soon. See the separate thread on plastic keris. And it would be rather difficult to tell the difference from photos on ebay. I personally would hesitate to buy any ivory just from photos.
Unfortunately, buyers were taken in by the very low opening bid for what they took to be real ivory
Alam Shah is right that the blade may have talismanic qualities, but it's not pamur but some kind of inlay. I have one that my father bought for a very low price from Semarang (Indonesia) 50 years ago.