The Nokia batteries which you can buy from any European Amazon for less than 30-35 € are FAKE. Even the most popular ones. They arrive in proper (original) packaging, they have genuine stickers and everything, but they are still not Nokia's. Check some comments on Amazon/forums.

Or look at it this way. Amazon sells "original" batteries for 10 €, whereas you can buy batteries from nokia.com for 30-40 €. Tell me another product from another vendor that you can buy 3 times cheaper from a different store than vendor's. You can't, it's not possible.

It is sad, because these batteries are really worth 10 €, but Nokia sells them for 30€+. I'm not saying that some unofficial ones doesn't come from the same line, but I wouldn't count on that.