A degree is the basic qualification for a PHD or even a MBA/ MSC.
I am sure you already know that it's expensive to do any recognized degree (I hope you are planning a foreign one) + for a PHD you have to do a UNIQUE project/ thesis, which is a hell of a deal! Basically you have to do something that was not done before

.
But here's the real case,
1) Do the same, if you are dead sure that you can capitalize on your PHD by getting a higher salary with a present/ potential employer.
I spent like $30,000 for my MBA but sometimes feel that maybe I should've invested that money in a business/ stock market because the returns are much higher and at the end of the day it's just a jewel, that's it.
Basically, with a PHD/ MSC, in your resume, you rather look scary to most employers

. That's because they do not want someone to take over them, down the line. So be practical and do not expect every employer to offer you a job with your PHD.
2) Given the amount of time sacrifice you have to make for the PHD, do it, if you really got too much time/ patience/ mind temperament in your hands. If not your personal life will be crazily affected and you will get quite dreadful down the line.
Anyway good luck with your choice!