True, experienced versus a newbie, yes there should be a difference. twenty years as opposed to five or ten years doing the exact same thing, I see no need for a diffence in salary. Just my opinion.
True, it costs alot to repair the cars, but the tech sure isn't getting that $80 - $100 per hour. I never knew what the shop profit margin was, but I'll bet it isn't too shabby. I believe the best technicians make in the area of $22 - $25 per hour, those are your union shops, nonunion are usually less, but not necessarily much less. And of course the labor rates are the same no matter what the tech is getting.
I'm no longer a professional tech, but I'll always call myself an auto technician, I think I'm entitled after 19 years. I don't miss it, but I am thankful for the experience.