^Yes, that is true! I think it’s an important point, especially for anyone whose interests cross both fields. For example, let’s say someone was interested in the economic impact of mass incarceration. That person could theoretically answer that research question from a variety of different angles - from a criminal justice PhD, a sociology PhD, an economics PhD, maybe a business PhD. I would personally strongly encourage them to consider one of the latter two (if they had the background to do so) because of what @peterquill said; the ROI there is just SO much higher than a CJ or soc PhD. Gradautes from mid-tier economics and business PhD programs are more likely to get academic jobs than graduates from pretty solidly reputed sociology programs.
At the same time, I do want to nuance my reply a little by adding that you should not get a PhD in something you are only mildly interested in. Since a PhD is about a career spent doing research in an area, it’s only going to be super frustrating to spend 6-8 years studying something you’re not really passionate about to get a job basically doing the exact same thing for the next 30 years. So obviously, for people who love economics and business getting PhDs in those fields can be potentially very lucrative. For people who are more in love with less lucrative fields…well, that’s okay too! Just go in with eyes open. (I can talk; my PhD is in psychology and public health!)