A few things.
1) Do not make the mistake by estimating cutoffs with the amount of people that went into BIGLAW. Not everyone that can get BIGLAW goes BIGLAW.
2) Where are some of these numbers coming from? From my data, they are pretty much all wrong - some are too high and some are too low. (My data comes from the CDOs)
3) $160k != all BIGLAW. While some markets are at $160k, not all BIGLAW is there. ($110k in Charlotte is BIGLAW, wtf conventional wisdom?) Also V100 != all of BIGLAW by a large margin.
4) There are not a ton of law students who are related to BIGLAW partners (but there are some). BIGLAW sucks, even for the partners. Most BIGLAW partners who could have children 22-25 quit 5-10 years beforehand. Further, your aunt/uncle/family friend will not likely be able to get you a job, although they could put in a good word for you which would help. (ok ok some BIGLAW partners can get certain people positions, but your numbers still have to be CLOSE to what they would have hired)
5) And to troll for my school, Tulane's "cutoff" for NYC was ~25%, for Houston ~40%, for Dallas ~30%, for NOLA ~45%. This is not to say anyone in the top 30% got Dallas BIGLAW - and further it is not to say a number of students at the median did not get BIGLAW in their home markets.