Amazon.co.uk has the region-free version for $33 + $7 postage/packing to U.S. = $40 shipped
(USD). You can use your Amazon.com account to check out.
Today only. Amazon
has the Superman: The Motion Picture Anthology Blu-Ray Box Set for $56
with free shipping. Set includes Superman The Movie, Superman The Movie: Expanded Edition, Superman II, Superman II: The Richard Donner Cut, Superman III, Superman IV: The Quest for Peace, Superman Returns, and a lot of bonus material.