When I was doing repair, the shops referred to the charge for lifting your set onto their workbench as the "bench press." It was usually given as a minimum labor time charge, such as 1 hour. You were doing well if you could get most repairs done in less than an hour. This depended on having both excellent diagnostic skill, and the experience to know what component was most likely to fail.

I ended up in an Apple repair shop within a government agency that served school districts. Since we didn't need to make a profit, we skipped the bench press, and if your Apple needed 15 minutes of work (typical), we charged for 15 minutes, while also letting you watch.

The pinnacle was TV repair because TVs were expensive but cheaply made and relatively simplistic. There were not many different ways that they worked due to the evolution of cost cutting measures. There were also good published repair guides -- the Howard Sams "photofact" series.

Stereos were not all that much more complicated, but a contemporary repair shop would suffer from lack of sufficient business to sustain a working knowledge of failures and repairs, and often obsolete or irreplaceable components such as output transistors. Paying $150 to sustain the shop, and learn that your set is unrepairable, are not far-fetched outcomes.

Also (in the amplified musical instrument world that I now inhabit), there's a declining number of good techs. For one thing, those guys can make a lot more money servicing million dollar industrial or medical equipment.