I was 28 years old when I entered university. With a background in law enforcement and military the idea of being some prep-school university type was not something I wanted to do. In my late 30s I received my Masters degree in computer science and saw a significant increase in perception of how my income was made. After the dot.bomb I was doing pretty good but shrinking staffs, horrible hours, executives who ran IT shops like they were slave pens, had me burning out pretty quick. I'd stepped out of doing the stuff I thought was fun and started getting paid to do stuff nobody thought was fun. I took a mid-university professor job, but they wanted me to get a PhD.
A masters degree is sort of like being a journeyman. You've mastered the discipline. A PhD is about defining the future of the discipline. There are a lot of junk PhDs out there. I've read their dissertations. There are a lot of good people with bad degrees and bad people with good degrees. Look at the trends to define rather than specific anecdotal evidence like my case. Don't mix up the history PhDs with the Computer Science or Technology degrees. What I would say was that I took nearly a 66% cut in pay to become a professor and full time researcher. I got the opportunity to do what I want, when I want, and how I want. After I got my PhD I ended up in one of the top engineering schools in the world, have done tours at major science institutions and government agencies, and turn down opportunities to work with others.
So, yes a mid life PhD can be a great thing for your career. You will find that people who don't have a PhD don't have any clue what it means to have one are either jealous or ignorant. A research based doctorate (PhD) versus an applied doctorate (DSc) will give you a broader understanding of what research is and how it is done. I was just speaking at a major national lab to a bunch of masters degree students about why they should get a PhD. I told them "don't do it." Unless, you love research, are willing to commit 5 to 7 years towards the goal, have your employers buy off, family buy in, and time management skills to die for. Nobody listens but the PhD is really about what you put into the effort. That will be obvious when you finish the longest test of your life. The dissertation. In the end that will determine whether it was worth it.