The labor rate when I started my career was $20.00/hour. Oil changes were $8.95, alignments were $19.95, and batteries cost around 30 bucks, if I recall correctly (and we had to add acid to them because they shipped dry).
Several years ago when I left the field, our shop was getting $135.00/hour. That does not in any way represent my pay, however. Most of that labor cost is due to daily operating expenses and the costs of regulatory requirement compliance.
My personal investment in my collection of tools, including storage and diagnostics, was well over $100,000.00, almost 20 years ago. Then factor in education over the years - there is no 'one course' one can take to become a Master Auto Technician. I took many comm. college certificate courses to keep up with new technology as it came about, and industry training usually ran around $200.00 for an 8 hour, two day course, with a suggestion of around 200 hours per year of technical training just to keep up with the changes to the industry.
I didn't have 'student loan debt' - I had continual training debt that had to be prepaid if I wanted to keep up. And I did. Over 40 years worth in total. Nowadays most shops want young techs that have an AA in Automotive Technology. I hear those courses can cost in the area of $20-30,000.00. For a two-year degree. Glad I didn't have that debt, too!
I just put a battery in my wife's car. Bought it at NAPA and did the job myself. That battery was $225.00. Plus the core charge. lol
As far as I know, there are no federal licensing requirements for mechanics like there are for say, electricians and plumbers. States and local jurisdictions may have requirements, though.