I dunno about academia, but I'm pretty sure the top-tier labs will hire you after a PhD if your research is good enough (i.e., enough papers in top-tier conferences) regardless of your age. For instance, Sriram Rajamani, who leads the program analysis group at MSR India, spent several years writing code before he started his PhD.
I'd like to reiterate that a PhD is not for the faint of heart. It's hard work, difficult work and you really need to be motivated to do top-quality work for 60 hours a week at near-sustenance-level pay while competing with the smartest people in the world to publish your research.
From the way you phrased your question, it depend on what you deem as a "good job offer". In terms of salary, the typical wage difference between Ph.D. and MS is not that big (in my field). You are also not earning for the time in which you pursue the Ph.D. (5 years maybe). As an example, most of my friends that did their M.S. with me went straight into industry. They are all in some form of technical lead/managerial role (higher pay) and had been earning a good salary the whole time. Also being a post-doc is not something you would want to aim for. It's more of a limbo position with poor pay. If you are talking about "interesting" work, then Ph.D. can open doors but it depends on your specialized area.
That being said, completing a Ph.D. will make you an expert in your field. If that field has strong industry ties, you will likely come out with many contacts through networking at conferences and events, possibly collaborating with industry members, possible research internships, etc. This will lead to job opportunities.
And as others have said, Ph.D.s are not for the faint of heart. For me, Ph.D. was similar to M.S., but with a longer term, slightly more risky project. So think about how you liked your M.S. experience. Your overall experience will also depend highly on your supervisor's personality, and how disciplined and motivated you are. I tend to think that I am a bit on the un-disciplined side, but I am very fortunate to have an extremely good mentor/supervisor. :)
If you want to chat further, feel free to post here or send me an email. :)
You don't need a high GPA, you need tenacity and perseverance and faith in your goals. And at the same time being able to take criticism, feedback and rejection.
You are not learning as for a BE or ME, you are creating new knowledge and sharing it with other academics with similar interests.
Postdoc and researcher positions are not well paid, very competitive and you need to have had some good papers published to even get a look in.
You must love reading, thinking and writing, re-writing and re-re-writing. This is where I still struggle. It's one thing to get things researched and implemented but another to write about it in a way that others will want to read. If your papers don't get cited, then it is hard to gain traction for researcher positions.
It helps to be a confident speaker at conferences, faculty seminars, etc. Thinking of it as an opportunity to market yourself to prospective future employers (as in universities and research labs).
My observation is that you either need to be in a good relationship or be willing to forego having one for 5+ years. Dating whilst doing a PhD is a huge distraction and could result in missing out on one or the other.
Finally, I think you need a Plan B. What you'll do if you don't like it, or like it but can't get a postdoc position.
PhD programs are very different from undergraduate (and most masters) programs. I wouldn't bother with one unless you are sure that you want an academic position, or a job in an industry research lab.
That said, research can be very fun! Just be sure that you know what you are getting yourself into. If you decide to apply, you may be interested in a series of blog posts I'm starting on the grad school application process:
On academia it's 10x worse. Do not fool yourself.