Earlier quoted context omitted.
You're taking that word way out of context. "Overeducated" here means getting an academic credential where it isn't necessary. There's nothing wrong with learning a lot, but that doesn't mean you need to pay $200K for a college degree.
Average student debt is $25K, hasn't been increasing that much, except in for-profit schools like Univ of Phoenix: http://www.theatlantic.com/business/archive/2013/01/student-...
Even then this doesn't tell you the cost of education (IE how much you + your parents are spending), only how much money you still owed at the end.
If it takes eating your parents 401k to pay for college, that's still very harmful, even if you only have 36k debt at the end.
Lastly, all the numbers are normalized to 2009 dollars, which makes them hugely misleading. If you look at the original data source, in original dollars, the debt load has gone up by ~50% in (They are also estimates, with 2009 being based on 17,000 out of 1.6 million degree earners. i'm too lazy to look up the methodology in the referred report to see if it's sane)