Amazon's current Blu-ray Boxed Set of the Week is for
X-Men Trilogy + X-Men Origins: Wolverine, which which can now be had for only $47.99 (60% off, or about $12 per movie). The price tracker shows that this is the lowest this compilation has been. This offer is valid through September 25.
Thanks to forum member "Tony5523".
Update
In an unheard-of initiative with a deal of the week, Amazon has further reduced the price of this set to $39.49, or less than $10 per movie.
Update 2
This deal has expired now.