Originally Posted by Freakscene
Manufacturing the right kinds of flint glass is not illegal in China.
Old lenses are generally expensive due to rarity and high demand once they become ‘classic’.
Yes, they are rare because the glass is unavailable. Particulary in Germany the environmental legislation is extremely strict. In the sixties Leitz produced its own glass, but those times are long gone. Some of their lenses contained six different kinds of glass with extremely high refractive indices. That is why the Noctilux f/1 is no longer produced. The Summilux 35mm steel rim is another example.
Maybe the production in China is less problematic, but usually other optical solutions are used, such as aspheric lenses. These produce a different type of image however.