I have had experience running a one-man repair garage.
Owners would expect a lower hourly rate than the majors/franchises.
They would expect me to be intimately aquainted with the tricks ,foibles and quirks of their particular make /model.
They expected me to carry every part for their vehicle ,at a more competitive price than the franchise.
They expected Ihad all the specialised jigs and workshop tools for their pride and joy.
Sadly, I only had 1,000 square feet, special tooling had to be done without/expensive universal substitutes used/the job contracted-out,-parts had to be ordered as required and their delivery awaited. Favours called-in,relationships "used" to find the resolution to some problems.
All this translates to a workshop cluttered with "work -in-progress", a huge phone-bill, a lot of running around and general admin time.....not forgetting the "wasted " time booking-in the work, collecting contact-info,discussing the work-schedule envisaged, exploring alternatives and presenting the customer with their options.
Anyone thinking the "retail" business of GA aircraft -maintenance will achieve "book-time" turnarounds is on another planet.
Oh, and what about the inaccesible nut that requires a special (and expensive) spanner It's rusted solid, shears it's stud which then necessitates extensive dismantling,drilling-out,thread-reclamation and rebuilding!
" To removing /replacing bracket with rusted nut £300"
It didn't usually happen, -you bit the bullet on a lot of the cost!
I usually worked~60 hours a week and hoped to book ~30
And that, friends, is one of the reasons that hourly rates are high...also don't forget things like Statutory holidays, sick-pay,redundancy,mandatory safety-tests/insurances/employee workwear etc. this all has to be factored into that hourly rate!