Why do reflecting telescopes cost less than refracting telescopes?

Answer 1

The objective lens of the REFRACTING telescope has to be a single gigantic piece of perfect glass.
The light being observed goes all the way through it, so any imperfection anywhere ... on either surface or
anywhere INSIDE it ... can affect the quality of the image. It also has to be totally stable and rigid, since
it can only be supported around the edge.

The mirror of the REFLECTING telescope only has to have a perfect SURFACE. The light hits the surface and
bounces off of it, so nobody cares what happens behind the surface. The mirror can be made of two-by-fours
or old crushed beer cans, and it can be supported by a solid rigging of carpenter's scaffold. Just as long as
it has a perfect front surface, we don't care.

For any large size you want for the objective element ... large enough to be attractive as a muscular
astronomical instrument ... it turns out to be much easier and cheaper to build a parabolic mirror of that
size than to build a perfect lens of the same size.

Answer 2

Reflecting telescopes tend to cost less than refracting telescopes because reflecting telescopes use mirrors to gather and focus light, which can be manufactured at a lower cost compared to lenses used in refracting telescopes. Additionally, mirrors are usually lighter and easier to handle than lenses of the same size, reducing overall manufacturing and transportation costs.