while the double Gauss has flaws, it delivers very good performance even in basic designs. And the design here is not a classic double Gauss. The back part is quite different. Also, it's only f2, not very fast for a 50 mm. That plus the liberal use of expensive glass types should do it.
my guess is Canon could produce the same for 2k. it's just a matter of market.
If you look at MTF, you will find an extreme sharp lens at f/2. No canon 50mm lens is that sharp at f/2. Why should I buy a Canon lens with f/1.2, when the lens is not better at f/2 than the Leica one and realy smooth at f/1.2 ? The lens is expensive but outperfomes all other lenses. Zeiss Macro-Planar is the best at about 1.2K€ at 50mm f/2.
At times of more than 100 lines per mm at the sensor, Canon professional 50mm lenses are soft at 30 lines per mm wide open. Canon should show a lens with an mtf of 120 lines per mm if the lens ist ready for the actural sensor.