I can just see the production financial guys cheering over being able to haul a few cheesy Western flats over from the lot, and plant them on a bare soundstage. Note other episodes where the sets are a few items floating seemingly on an endless plain.

Irwin Allen cut corners in a similar manner, and many were the episodes from various Allen SF series where the set was a computer or other gadget sitting on a floor, brightly lit, while the entire background (no doubt another bare stage) was completely black. A few examples from "The Outer Limits" come to mind, too.

The Star Trek production values are often sneered at by modern kids used to being able to pull things out of a computer for a nickel, but the producers worked creative marvels to turn out that show on a weekly basis with the "stone knives and bearskins" of that time. Some of McCoy's instruments were salt shakers. Costuming and "futuristic furniture" came from studio storage, or garage sales.