While I agree with you that debt load is a major consideration both in choosing a school and in choosing a career after graduation and bar passage, I don't think it is reasonable to portray the alternatives to BIGLAW as ones that only pay $60,000 per year a full *decade* after graduation. To me, that seems unreasonably low for any lawyer with a shred of ambition and a modicum of competence.
The average starting salary, for most schools, in the public sector, is around $45K. For government jobs, it's usually a little higher, more like $50K. Everyone doesn't end up with the higher-paying jobs. A DA may start out making $45K--I don't think it's unreasonable to assume that 10 years later, in the same job, he's not going to be making that much more. A raise, with cost of living increases, just doesn't bump you up that much.
The average starting salaries in the private sector are so high because of BIGLAW. If 20 people out of a graduating class of 200 are making over $125K to start (that's probably overly generous), then of course the average salary's going to be higher, even if the majority of your class is making $50K at a small firm.