A few things:
1) You May know how to fix cars but you will have some learning when it comes to sales and business. That’s ok, but recognize that and grow your skills in those areas.
2) You need to be cool with sending price shoppers to other shops. That’s the symptom of a trouble customer.
3) It might help to have a few word tracks. When questioned about parts prices I’d say “you can buy a steak at Walmart for $10 or a steak at a steakhouse for $40. This is the steakhouse.” Most people understand that and you’ll be surprised at how many people will chuckle and give you the work.
4) Inspect every car and do not break down the prices for each repair when talking to the customer. Simply tell them the work that needs to be done and then say “looks like it’s gonna run about $3200 for everything, I can start on it today should I get the parts coming?”
if they can do it, cut the job down to the safety items for them and repeat the process with the smaller job. It’s nuts, but it works. I learned that from a guy on here 10 years ago.
That’s the fastest way to fix your profit problem along with a strong parts matrix like mentioned above.