I dunno... I do pretty well selling VHS tapes made 20 years ago. And since DVD does not degrade in quality, I can easily see certain titles commanding collector prices over the years. Which titles? Well, that requires some research, but watch eBay, and you will soon realize there is a pattern.

Yeah, OOP Dvds are worth money for the same reason that VHS versions of movies that are not yet on Dvd are sometimes worth money. Most movies have fans that want to own their favorite movie so they can watch it whenever they want.

And if you really want to have a DVD go up in value keep it sealed. Even if there are alot of a certain DVD it can be difficult to find a new copy