That's really interesting, and I'm not surprised to hear it.
There was a study a while back concluding that it doesn't matter where you go to college - provided you major in STEM. It's a little more complicated than that (attrition rates, quality of curriculum), but overall, there is some truth to this - if you want to get a good job and keep costs down, majoring in engineering at a reputable state school can be a good way to go.
There is an interesting corollary to this, though - it does matter where you go to college, provided you don't major in STEM. This might explain why "elite" US college students are so allergic to engineering. Why go to Harvard if it doesn't provide you with any advantage. If computer science majors from San Jose state have access to the same jobs, what good does Harvard do you?
If you go to an elite college, you can major in economics and go to business school, or hell, major in international relations and go to law school. Jobs prospects for lawyers aren't generally great, but pay and prospects are very good for people who build a network at an ivy and go to a very elite law school.
So your comment about a slate-mining town may be particularly relevant here. People who perceive college from a low income perspective see no point to majoring in Art History, because their chances of becoming a six figure salaried director or an art or cultural institution are basically zero. For a Harvard grad, however, especially one form an upper middle class family with the right connections, it may be a very achievable possibility.
Similarly, why would. a Harvard grad be a senior CRUD bug fixer for 140k a year when he or she could run a nonprofit or cultural organization for a similar salary?
Perhaps the value of elite colleges isn't so much that they can get you a higher salary, but that they can give you a path to a higher salary in culturally interesting job paths that are closed off to most of the populace. Harvard allows you a crack at that salary without having to be a senior CRUD bug fixer.
As an aside, I think one big thing may be overlooked in the "it doesn't matter where you go if you major in STEM" study, because there's a lot under the hood if you only consider salaries. Just as there is a big difference between being a senior CRUD bug fixer for $140k a year and the "director of the American Heritage Film foundation" for $140k a year, there's also a difference between ostensibly similar titles in tech. It could be that elite tech graduates don't show a big difference in salary between grads from less celebrated schools, but do they end up with more autonomy, fewer deadlines, more interesting and exploratory work? "Machine Learning Specialist for Election Results analysis" for the NYTimes is a very different job from "Manager of Payroll and Benefits Data Migration" for a bigco. I'm not 100% convinced where you go to college plays no role in this.