Why Japanese calligraphy brushes are so expensive

A handmade calligraphy brush, custom made for a master calligrapher, can cost over $1,000. At Hata Bunshindou each brush tip is made by a single artisan. It’s a delicate process that can take over a month to complete. But you can find a beginner calligraphy brush for less than $15. So what makes these brushes unique? And why are they so expensive?