But extensive prosthetics were still much more the exception than the rule. And The Twilight Zone and The Outer Limits usually involved only one outlandish element - They didn't have to create an entire future world from scratch every week like TOS did. Most episodes took place in the present day. So I suspect that they were able allocate more budget to the makeup department when they needed to. And heck, sometimes even they cut corners - the classic Outer Limits episode "Demon With A Glass Hand" has guys in black turtlenecks with boot black around their eyes as the alien Kyben.