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Unfunded grad school is pretty much never worth it for that reason, especially for non-STEM fields (but even for STEM, it's still pricey enough that it probably isn't worth paying full price). Med school is also pricey, but high salaries make up for that, and what I've heard of law school is that it isn't worth the cost if you aren't going to a top 20 school.
But as for specifically undergraduate education, I do think the financials make it worth it in many cases, but it's misleading to generalise across all majors. 30k of debt for a computer science degree is likely worth it, sure. Is it worth it for an English degree? Debatable, but 30k of debt at least isn't going to financially hobble someone for the rest of their life. Is it worth paying full sticker price (if e.g. the student doesn't qualify for financial aid) for a sociology degree? I think that would be dubious.