What characteristic makes refractors substantially more expensive than reflectors of equivalent aperture?

Answer

The laborious grinding and polishing required for both sides of the lens to precise curves.

The high cost stems from the intensive manufacturing process involving grinding and polishing both lens surfaces precisely, compounded by material waste from flawed blanks and the frequent need for expensive, specialized glass types.

What characteristic makes refractors substantially more expensive than reflectors of equivalent aperture?

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