opps ... i ignored the original question...what is so special about the legendary japanese sword..... I held a 17th century katana last week valued at $10k....oh my. It's like holding something sacred.... you become very aware of the history and can see the skill that was required to make it. I make swords myself and I am aware of what makes a good sword [there is so much more to it than my quick short reply above]

If you mean are Japanese katana the ulimate sword... no not really but the techinque and skill involved is awe inspiring. The differental temper was a monumental technical feat of engineering for that time period. In the hands of a trained a Samuraiit is a weapon of massive ability.... there are viking blades that are stronger and tougher but a japanese blade it a pure cutter... the physics are incredible

Metallurgy wise modern swords today are better. I am not refering to the mass produced crap you can by. BUT the skill of a Japanese swordsmith if that of a craftsman and an artist. The skill [ to me ] makes the difference

A good high end modern custom made sword can run $3000 to $15000 depending on the smith

Good swords flex

yup... and stay straight after they flex. Flexibility is a part of the toughness factor and at the same time are hard enough to hold a sharp edge.

But even a quality blade deserves to sing and be listened to.

Depends.

On another note, I think the Japanese blade is made of two parts