Two years ago I started to repair expensive equipment as a hobby but quickly dropped out of it.
While some repairs are really easy even at amateur level like myself, some repairs are really difficult (though I do have hot air soldering station, oscilloscope, signal gen, spectrum analyzer, etc.).
The main problem is this:
Exchanging a 50 cents part that requires four solder points, even small ones, is a piece of cake.
But if the PCB belongs to a 5000 Euro equipment, any error on that 50 cents part might cause a 5000 Euro loss!
And it often starts with a solder point, then suddenly too much heat and the PCB trace pops up, then you seek another point on that trace and suddenly you realize you screwed up.
Taking this risk for free, for friendship, for a small amount of money is simply not worth it. If you make the repair happen: yeah! You are a great guy for 5 minutes. If you screw things up, which happens in seconds, you are an a**hole for the rest of your life.
I guess this is the real reason why so many people refuse to do the job.
Regards,
Vitor