>>63889941
Swords in Japanese culture have a mythical status, with each Katana being its own Kami. Swords are deified, hence the propensity to want to protect and revere them above what you'd normally do for a tool you want to trust your life too.

Also most swords were melted down and seized over the many sword hunts of the past few hundred years, so the surviving examples are naturally going to be better preserved due to scarcity - especially if they're from a famous swordsmith. Many swords are worth more than a house in Japan.