Just some experience in this area I'd like to add as well. I've done laptop repairs on the side for people for about 15 years now for ref. A long time before that I did prod line rework on milspec kit. Some thoughts:
1. Component level repair is not worth it at all. Not even slightly. It's expensive in time, research, tools. The success rate in the short term is not great. The success rate in the long term is not good. I would ONLY ever consider doing component level repair now if it was for data recovery and temporary and the hardware was disposed afterwards. The main problem you have to ask yourself is "does it actually really work afterwards or does it look like it does"? In fact one of the worst things I saw was water damage where someone had bodge soldered the memory bus on the machine. It booted into windows but blue screened once an hour. Didn't even run memtest86 once without errors. Straight in the trash. That's what you're risking. All it takes is takes is a enthusiastic user to run a defrag and all their shit is gone.
2. I refuse anything that isn't Apple, Lenovo, Dell or HP now because it's impossible finding out what crap the laptop is assembled from. Everything is made by the lowest bidder apart from the mid-high end business laptops. Anything that is consumer junk bought at retail goes straight in the trash unless it's basic upgrades or noddy stuff like new batteries, keyboard or screens.
3. As much as everyone shits on Apple, they have nearly the best repair outcome (only surpassed by Lenovo) becuase the hardware is pretty standard across the board, easy to get hold of, repairs are well documented and there's not a lot of stuff in their kit. It's really easy to to repair. I'm talking laptops here. iPhones are pretty easy to repair as well. I've done tens of them now. iPads are the only sticking point (pun intended). But the parts are going to cost you real money because there is a high demand for parts.
4. The second most expensive part of any repair is software failure. Reinstalling OS and getting people's shit back costs nearly as much as replacing the computer.
5. The primary expensive part of any repair is DOWNTIME. Not a lot of people realise this. If you have to lose your machine for two weeks for a repairer then that's two weeks lost income. If you can't afford to lose it, you can't afford to own it.
Just as a note I charge £60 an hour for repairs I do, plus parts, plus incidentals, plus VAT. The last person who came to me had a Lenovo T450 with a smashed screen. The screen cost me £45, it took an hour to do it plus an hour of "fix some random stuff in windows". That was £198 inc VAT. You can get a refurb T450 same spec on ebay for £239. Why bother? I mean I'm going to take the money if someone asks me to but why?!?!
Component level repair doesn't factor in this at all because even when it comes to "2015 macbook pro" territory, if you really need to kit then component level repair, software failure, downtime are orders of magnitude more expensive and the outcome from anything other than FRU replacement is iffy as hell.
The big problem I see is that Louis Rossman has made a lot of noise resulting in a bit of a repair personality cult so everyone looks at component level repair as worth it. For 98% of cases it isn't. For 1% of what is left over it's data recovery. For the last 1% it's personal interest.
Edit: just to add I have two Lenovo T440 units that are identical as my daily driver machines. They pay the bills. They are now both heavily modified. If one dies, it gets recyclable parts removed, goes on ebay and the other one comes out of the cupboard and I carry on. I then buy another refurb and apply the same modifications to it in my own time. Mods include FHD display, different touchpad, extended battery, removal of camera and mic and mSATA battery, replacement internal battery, memory upgrade. These are all FRU replacement steps and take about an hour to do a whole machine of mods. Downtime and software downtime are minimised here to a max span of 1 hour which is the optimisation point. Time = money