I've had talks with a few PhD's and a few masters and bachelor's in mechanical, electrical, and chemical engineering. Both in my current industry and at my university.

I am not doing a Ph.D, so take my comment with a large grain of salt. But the consensus I've gotten from those I've talked to about specifically engineering disciplines is:

• Get a Ph.D if you'll want to become a university professor, or get into research/R&D at national labs.
• Get a bachelor's and/or a bachelors+masters if you want a normal career anywhere else in any industry. Many companies have programs where you get a bachelor's, go get a couple years of work experience at an entry level engineering job, and have the company pay for the master's a few years later as you can take a masters program part time.

The trap I've had described to me is that Ph.D's often become over qualified for typical industry entry-level positions, and the number of Ph.D specific postions much narrower and specialized, making job seeking after graduation actually harder than if you simply got a normal bachelor's with one summer internship. Of course once you get in your salary will be much higher- offset by some degree by the extra 100k in student loans you'll likely have.
Ph.D's specialize in much narrower fields than undergrads, so lateral mobility is reduced once you're "set" in a specific field and industry. It's also incredibly difficult to complete compared to undergrad, and will require a ton more of your time- time that could have been spent developing earning potential and a normal life.

I know it's definitely not for me- I don't even know if I could survive long enough mentally to go through a master's program. But your mileage may vary, of course, depending on where you want to take your life.