I think the term "in the vault" is a bunch of hype. You can purchase Disney videos at resale shops and flea markets for anywhere from 50 cents to $3. Disney re-releases all their movies with a few changes or enhancements on DVD. They want to sell movies!
This is all a marketing scheme by Disney, but you are right. There is a demand for disney videos, since Disney vaulted. The Value depends on the demand.