That depends on your PhD research area (even if in CS) and country.
In many countries PhDs are only valuable in academia and industrial research institutes, but your salary is capped quite a bit long term.
In Asia a new grad fresh out of college is seen as more employable than a new PhD grad by most companies and salary differences would be minimal. I wouldn't recommend doing a PhD if you're out for a high salary there.
On the other hand in some European countries just having any PhD degree will open up career paths and salaries unavailable to non PhDs regardless of actual skills.