there is also a big difference in selectivity for MDs and JD

The number of lawyers accepted and churned out every year is vastly higher than the number of doctors. As such, the selectivity of the applicant pool is much higher for doctors (~15K spots in the US for <50k applications).

I suspect that if you compare the data on the top 15K lawyers in the US each year and the doctors, the competitiveness of the applicant pool would be around the same, but income would be quite skewed in favor of the lawyers.

If you compare the total law graduate pool to the total med graduate pool on a given year, I suspect that the larger bottom end who go to uncompetitive law schools (of which a med school equivalent does not exist in the US) would drag down both the income of lawyers, as well as the overall competetivenss of the applicant pool.

The reason that 150K is not assured with law school is the prevalence of lower quality law schools and a bevy of lower quality applicants. (which itself is a function of a law school being a money making proposition, whereas a med school is not - at least not nearly to the same degree - more resource intensive per student. Adding more students equals more doctor teachers in clinical years, which does not exist in law school. Just can add more students to the classroom).