I am an academic clinician-scientist with an MD and a PhD.  So I do both jobs.  I sympathize with your salary and wish you could earn more doing academics.  But doing both I can assure you that the 500K is tough and draining while the academics is what I do for fun.  You have a great job and your life wouldn't be much better with more income and all the sacrifices that come with it.  Doing a PhD is not the same as doing a surgical residency.  Don't compare them as "education" by years.

We docs need to stop complaining about our income - nobody wants to hear it!