Is the possibility of increased salary worth the cost of graduate school? (MBA)
Depends on major
Who you know and the breaks.
Statistically yes but each persons situation is different.
I'd say yes for an MBA but not for all people and not for every degree. It really depends on what you plan to do with it.
I have a cousin with an MBA from Harvard. It was very worth it for him. On the other hand my graduate degrees in physiological optics lowered my salary because teaching and research pays a lower salary compared to that of a private practice optometrist.