Case knives retain high prices because they're considered by many to be the foundation of the pocket knife collecting hobby. Case hand-crafted knives are popular as gifts that can be handed down over generations, and like any collectible item, prices are reflected by what collectors are willing to pay.
W. R. Case and Sons Cutlery Company began making knives in 1889 in New York. Since then, Case knives have become so popular that a Case Collectors Club exists, and with 19,000 active members in 2015, it's the largest knife collecting club in the world. In 1993, Case was purchased by Zippo Manufacturing Company, makers of the world-famous and similarly collectible Zippo lighter.