It doesn't really save on salaries, though, unless the company is so small that it doesn't have enough work to take up the time of both a full-time full-stack d

It doesn't really save on salaries, though, unless the company is so small that it doesn't have enough work to take up the time of both a full-time full-stack developer and a full-time operations person and can replace two people with a single person who does both jobs. It costs more because someone with both skill-sets will demand a higher salary than someone with only one of the skill-sets.