
GoHardDrive.com has the White Label 640GB 7200 RPM 16MB Cache SATA 3.0Gb/s Hard Drive for $45 - $11 shipping =
$56 shipped. It uses a new 2x320GB platter design. They hint that it is similar to the Western Digital Caviar SE16 WD6400AAKS (which probably means it IS that drive).