Having a pharmD absolutely gives you a leg up for multiple reasons:
1. You can get hired as a staff pharmacist by a company/firm and then have them financial provide for the law education in exchange for a contract to represent them for X amount of years.
2. More simply, you will win more cases because you are more knowledgeable, which leads to a better career.
3. From all the Patent and Pharmaceutical Lawyers I have met, contacted and heard of- I would say about 60% have their pharmD and all seem to be in a better position than those who don't.
There are a lot more PharmD/JDs out there than you would expect- so obviously it is not a waste.
As far as salary, it strongly depends on your ability and subsequently your job placement. I know some PharmD/JDs in academia (probably not the salary you are looking for) and some with the corner office flying around the world constantly, living the dream. So, it varies. Any job in Pharma typically starts lower than retail/hospital PharmD jobs (about 70k) but has so much more potential to increase than the conventional PharmD route, especially considering the decreasing shortage of pharmacists among us, the salaries may stay where they are for quite some time or worse.
My best advice for you is: If you love pharmacy but feel like you want to do more with it than retail or hospital- not just because of the salary issue- then take your LSAT and see how you do. If you get above a 160 and have a solid GPA from Pharm school, apply to law schools and see what you get into because the reality of it is: your future in law is a lot brighter if you get into a good law school.
Let me know if you want more advice about this in the future. I am a pre-law pharmD student who will be following this path and I am constantly learning about it myself. I am currently talking to/emailing 5 pharmD/JDs that I made connections with at the annual APhA convention and will be attending the annual American Society of Pharmacy Law convention in November, so if you would like me to keep you informed if I learn any new facts- let me know I would be happy to help because I am going through the same thing as you right now.