They need to pay a person, but that person can start with a machine-translated text and only needs to edit the parts where the machine failed. So the same amount of text can be translated using fewer translators. Although the machine can't do everything a human translator does, it can still partially replace them, just as technology has partially replaced humans before (think a dozen guys with shovels vs. one with an excavator).

Well - sorta in some use cases; my suspicion is that translators working in this way find most of what the machine can do marginal in value.