wow pointing to a site that on a regular basis goes oops our numbers for BD where wrong and way lower then usual. What next

On the other hand there is a reason the HD DVD is slightly lower there are no good new releases. If on the other hand you compare the same title on BD and HDVD (let's say the departed since it is on the same page you linked

The Departed [Blu-ray]
Price: $23.95

and

The Departed (Combo HD DVD and Standard DVD) [HD DVD]
Price: $27.95

someone with both players that wants the movie must pay more for the HD DVD

now a third rate title that has been on the shelf for almost a year like Serenity will be Serenity [HD DVD]
Price: $19.95

but then you are comparing apples and oranges


the average price on HD DVD (as computed there) are a bit lower but that is because it has in its mix a lot more of mossy titles that no one is buying