Geez, why does there have to be a "culprit"? Warner put a $29 SRP on The Wicker Man, but a $40 SRP on The Departed, which came out a couple weeks later. Probably, Warner recognized that demand for The Wicker Man would be lower and priced it accordingly.
I doubt it. Like Jason said, The Departed was a $40 combo (and more expensive than it's Blu-ray counterpart), and the next Uinversal combo is The Good Shepherd, which is also $40.