You are paying because it is an actual usable lens, not a telescope.

Telescopes have a larger market and it balances out the development and production costs.

This lens took over a year to grow the fluorite. It was made by hand. And there are extremely few produced. So hence cost will be exceptionally high.

It be like saying why is the Ziess Octus costs as much as it does compared to other very good offerings.

And telescopes are typically not designed for photographic use. So many times their Bokeh is not as nice and the way it renders an image might not be as good.

But in places like the Olympics, high profile news agencies ect. The cost of this lens is on the level of other extremely high end gear. And for some people, who are well heeled, it is a dream lens.