What are "worthwhile" contributions that I could make to today's society as an astrophysicist?
I want to get a doctorate in astrophysics but I don't want to do all of this work and spend all of this money/ pay off loans for several years if I can't do something worthwhile with it. stem women-in-stem astrophysics stem-education stemcareers
Consider assisting serious people who seek to establish permanent settlement on Mars. http://www.mars-one.com/news/press-releases
Also, I greatly admire Neil deGrasse Tyson - With his smarts he entertains, educates and celebrates the beauty of the Universe for all to see! In my opinion he does a very fine job of making science study worthwhile!
Go for it! The possibilities are limitless :)
In short, it seems that astrophysics is a more esoteric way of bettering humankind through advancement of our collective knowledge. It's the seed corn to future advancement.
About your money concerns, here is information from the Bureau of Labor Statistics.
A note about borrowing money for a degree: try to keep your education costs so that you do not borrow more than your expected first year salary.