DVDs are more expensive for exactly one reason. You pay more for them. Prices are not set by cost, but rather by demand. If DVD buyers are less price-elastic than buyers of entertainment in other media (which early-adopters of technology tend to be), the price will be higher.
Majormd’s weird experience with Wing Commander results from another strategy. Whenever a new title is released by a movie studio, the studio has to decide whether to price it to rent or to own. If they think the title has potential to sell in large quantities, they set a suggested retail price it in the $16 to $30 window. If they think the title will mostly be rented, they slap a retail price on it of $110 or so, so they make money by selling copies to the video stores at the also-higher wholesale cost.
This pricing model is changing (slowly) as alternative media (DVDs, for example, which because of the small size of the market are almost never priced for rentals) and the changing economics of the video-rental business cause studios and video stores to explore new ways to do business such as rental-revenue sharing.
But there are plenty of examples of the old pricing model out there, and Wing Commander is obviously one of those. The Aliens situation that handy found is priced for retail sell-through. I have no idea how the OP found a $78 price, unless it came as a “Director’s Cut” or some such.
Livin’ on Tums, Vitamin E and Rogaine