I don't consider a PhD to be in any way equivalent to a MBA. As far as training ...

I don't consider a PhD to be in any way equivalent to a MBA. As far as training goes, a PhD is about how to do research. The result often in fact is a step down in salary. Plus it seems to be very difficult to find any recent data on salaries.

This, from 2013 (!), says PhD salaries are about 15% more and signing bonuses are less. (https://www.stanforddaily.com/2013/10/22/salary-ranges-for-s...)