Geography plays a major role too. Here in East Tennessee, musicians of all sorts are a dime a dozen, and there's always tons of used gear to be had, so a lot of times stuff that has minor issues gets tossed because broke musicians can find cheap used "new" amps easier than paying a tech to fix their old ones. That's where most of my stuff came from. Every single repair person I know without exception has either stopped doing it for lack of income or retired, generally the former. When you're buying parts and then customers flake and leave you with an amp that you can't sell for the money you have in it, you can't make a living, and that is more common than not.
The ENTIRE purpose of the "bench fee" is to offset for other non-paying customers. I quit years ago before things got THIS bad. If you're a non warranty service center (and sometimes even if you are), a board to repair a switching amp can literally cost more than another of the same type sitting new on a store shelf! I can't tell you the number of times I'd get an amp on the bench and find a problem, give the customer an estimate and a timeframe to which they would agree, and then end up with a new amp for myself, because "Man, I just can't afford that now. Earl-Bob sold me his (fill in the bank) amp and now I'm broke." ...and the only money ever collected from four or five hours work and $60 in parts was the $30 bench fee. Just charging up front for parts weeded out half of my business, and I was glad to be rid of it. But when those are the only jobs you're getting, you can't do it.
I didn't have time to get warranty certification for companies because I was too busy working my REAL job, but I was better than ALL of the so-called "service centers" locally, which was a two-edged sword. I got stuff they had tried to fix and ruined and I got the customers that they knew better than to deal with. When the economy went bad in 2001, those became the ONLY customers. I was working full time and playing in a band as it was. I didn't have the time to chase deadbeats for junk amps. I also did work in other wide-area circles that WAS warranty work in GOOD service centers, and the story was the same there, except you were always waiting on amp companies to reimburse you and they had even more excuses than deadbeat musicians.
With a relatively low cost of living, this area pays wages that would be well below poverty in any major metro area, so everything effectively costs more because of it. I got whines about a $30 bench fee 12 years ago; in a major market, double that, and for anything complicated, quadruple it. Parts cost the same here, but people have less money to spend, so they're more likely to just flake. If you ever want a laugh, get on the Knoxville Craigslist page and look at prices people want for JUNK. MOST of the stuff is nearly new, probably broken, and priced higher than it was when it was new, last week.
I have a buddy who ran his own music store in Greeneville and did circuit (a route he made- not literally electronic circuits) repairs for a number of honest local shops (One shop was infamous for being crooks and they finally closed last year after decades of ripping people off and having them love them for it.) and he finally had to stop because costs wee just too much even with all his standing certifications and service center status. Add hostile manufacturers unto the mix like Fender, who is TRYING to get rid of all their independent service providers and has been for about five years, and it's stupid to even try. One former service center/music store dropped Fender entirely because of their new requirements for being a service center and dealer. They now charge WHOLESALE prices that are near the RETAIL of places like Guitar Center and Musicians Friend.
It's all because of money and greed. When an investment group buys an MI company, it is almost ALWAYS a very bad thing, and almost every major MI manufacturer is owned by an investment group. Mesa, Yorkville and possibly Peavey are still self-owned. Gibson doesn't count; The only electronics they put out are in their robo-Fireturds.
