No, no particular technical difficulty, just another step in gradually falling prices. We have seen drives hit $0.39/GB as well with standard Amazon.com pricing. The Crucial M550 (a bit faster) is at $407 for 1TB model today, for example: http://amzn.to/1kBpIs1
Good drive, for sure, but keep in mind that the Crucial MX100 broke that barrier at its launch in June (and at $0.44/GB).
If it wasn't for Newton, we wouldn't have to eat bruised apples.