Assertion: telescope's mirror | /r/HasProperty | cheaper to make
Facets:
value: a lot
type: DEGREE
Source sentences:
text: Dobsonian/Newtonian telescopes have a big advantage over telescopes with lenses such as refractors and Cassegrain telescopes, as mirrors are a lot cheaper to make than lenses.
text: Because mirrors are cheaper to make than lenses, it is a better option when considering price vs. aperture.