Don't forget that a PhD makes it more difficult to get some kinds of jobs. An intermediate or low level developer job may pay more, but if you have a PhD the interviewers are going to question why you are applying for a low level job and be worried how long you will stay. So in some respects a PhD reduces your employability (though you can always lie and say you never got the PhD, though it is kind of hard to hide on a resume without leaving a time gap, which makes you seem even less employable.)