We love how these knives have a mythical vibe in them but basically just uber high level of craftsmanship. The combination of high demand and low supply/rarity explains the astronomical prices (and still increasing). Active makers like Kato and Shigefusa have a backlog of 3-5 years!
What is a honyaki? Honyaki (literally "true-forged") knives represent the highest level of craftsmanship; only a few skilled craftsmen in Japan can make them. These craftsmen employ techniques similar to that of traditional nihonto (Japanese sword) where a single piece of steel is differentially heat-treated. Why are these blade so expensive? Making honyaki knives is a challenging and time-consuming process as it involves a high degree of skill in temperature control and forging. Failure rate is quite high---some blades will crack or will severely warp in the quenching process. The additional labor in sharpening and finishing also contributes to high prices.