Is there a non-materialistic reason to go to college? Couldn't we all theoretically get by making min wage? Is working to earn more than the absolute minimum required to support yourself materialistic as well?
Would it make me sound too much like a college professor to suggest that one non-materialistic reason to go to college is to learn something, to be introduced to unfamiliar important ideas, and to acquire some of the skills required to be a good citizen of a democracy? Perhaps that's missing the real point of your question, which is less about going to college than about earning more than the minimum wage. In the United States, the "minimum wage" set by law is not the same as the minimum required to support yourself. Many people who earn minimum wage in a full-time job find themselves with insufficient income to support their families. Again, perhaps I've missed the real point of your question, which is whether it is materialistic to earn more than the minimum wage. I certainly agree that income inequality is morally dubious. If you find yourself earning too much, then I suggest that you donate your excess earnings to a worthy organization -- such as your local public university.