I'm not bothered by cantilever material, the final arbiter is the overall performance in your TT/arm/system. FWIW the previous owner of my Final Audio Parthenon had both the Sony XL88D ( one piece diamond cantilever ) and Dynavector Nova 13D ( 2 piece diamond cantilever ). He kept the Dynavector, returned the Sony XL88D. Final Audio also offered 1 piece diamond cantilevered MC's designed by Yoshihisa Mori based on the Sony design - 1 with full 1 piece diamond cantilever/stylus, another with 1 piece diamond cantilever/stylus but the cantilever in the latter sample was half length with aluminium sleeve.
Over the years diamond cantilevers have been used by several lesser known ( in the west ) boutique cartridge manufacturers, but it is only one component in many that produce the final result.
As regards value, the incremental cost of the diamond cantilever on the Koetsu is $5k - even a cheap car would lose that value in 1 year, but you should get 3-4 years use out of the Koetsu, so it's all relative.

