For somebody on the fence about getting a PhD (in robotics/ME), is it any more worth it if I'm already in a top school (MIT) in a fully-sponsored MS program and have a relatively easy way into a lab with a professor I'm interested in?

My main concern is that I'll be over 30 when I graduate and while I'll be extremely proud of myself, have a PhD from a prestigious lab at MIT, the level of commitment (only adviser I like is an extreme hardass, I know it will be a painful 5 years) and lack of money I'd be making (45k/yr) at an age I'd like to find a potential wife at turns me off. Right now I'm getting offers for 140k/year from major companies and having never really made money, it's pretty fucking enticing to just finish this program up and finance a new porsche 911