My figure of $40,000 came from discussions I had with a number of undergraduates. I would guess that this represents about the most debt that undergrads toted up. I remembered it because it depressed the hell out of me at the time. Most of these kids had very poor skills and were headed for a middle-management job at Sears in the best of possible worlds. I just didn't see how they could pay off their debts with those employment prospects.
I have the same attitude about debt as you do, and have, so far, never been in debt. My total college debt, through BA, MA, and Ph. D was zero -- and this with a parental contribution of ....zero. However, when I was going through school, it was possible to live on very, very little money. This is no longer true.
The people I know who are paying back educational debt do so for a very long time....like ten years or so.
Joanna