I get where you're coming from, but on what are you basing your advice? An MBA and a Data Science degree are entirely different things that require entirely different backgrounds and prepare you for entirely different careers (depending on concentration). And you definitely shouldn't start a Data Science program, and MBA or really any grad program without knowing exactly what you want your career path to be afterwards and how you can utilize your grad degree to get you there. Any master's degree is not worthless in and of itself.

The question to ask is how does this degree get you to where you want to be? If OP wants to continue on to non-profit management, they can make fairly good money ($100k+) in development, tech, administrative, policy, communications, etc positions at a ton of non-profits in large cities in the US, and an tuition-free economics master's isn't a bad way to get there.