Well, from my perspective, a masters was absolutely worth it. My pay raise paid off my degree in 8 months and I can have a new job doing what I love in about 2 weeks if I get tired of where I am. But then again, I'm a computer scientist. No idea how it works in your field. But, here's what I did in addition to that degree that was worth about 15% of my hourly rate.
I started a consulting company.
A lot of bosses like to see that you've started something, managed something, can manage your own time well. If you can run a company at a profit, you'll increase their profits most likely. May not work for everyone, but it got me a lot more job offers than before.