To keep costs down, most episodes of Star Trek were filmed on Earth instead of on location in outer space.
Also, the Ferengi drive a hard bargain, and could not be signed up.
So they hired human actors with prosthetic foreheads on their real heads.
Lately, costs where cut by another 50% – they're filming them on a half-O deck now.
Space. The finally affordable frontier.
@dgar I remember watching a documentary about the Moon landings, and in the credits it said:
Filmed on location.