I imagine it would have been even more expensive and unobtainable in Japan -- they historically had no source of quality iron and most was laboriously refined f

I imagine it would have been even more expensive and unobtainable in Japan -- they historically had no source of quality iron and most was laboriously refined from iron sands and was of poor quality. This is also what necessitated the development of advanced metallurgical techniques such as repeated folding and blending of different steels to compensate.