It's typical - conservative even - for lawyers who end up going into BigLaw. $160K starting salary will let you pay off even a couple hundred grand in loans in just a couple years.
This admittedly is only about 20-30% of law school graduates, but in a survey of net worth, dropping the 20-30% of data points that are most likely to have high net worth will skew your average significantly.
I think your information about the cost of legal degrees and the prospects for new lawyers (on average) is woefully out of date.