When you make HUGE price tags to repair items, people are going to repair it themselves. I previously worked for Lenovo/Asus repair depot. To replace an LCD was over $300. Part on eBay is about$60 takes maybe 10 mins depending on the model. So when you flease the customer long enough, they attempt it themselves because the $300+tax or buy a new one for $400. Most think I'll give it a shot for $50.
I think the biggest issue for any repair shop is they can't deliver "I'll give it a shot" service. If it doesn't work, people aren't very likely to pay you $50 or even believe you really tried at all. If it turns out something else is broken too, they won't be very happy being stuck with a bill and a still broken machine. In fact you could end up in an argument about what was broke or if you broke it. If you do it yourself as a last-ditch attempt before throwing it in the trash you got nothing to lose, but deliver it to a repair shop and the customer will never accept that. They want a quote and a repaired machine for that price and you're burdened with the risk of delivering that. If those parts on eBay turns out to be faulty or shoddy knock-offs that don't quite work right or have quality issues that could become your problem too. Also if bad shit happens shortly after it comes from your shop they'll try to blame it on your repair, whether it's actually correct or not.
All of this starts amounting to quite a bit of overhead, if someone comes in with a machine you probably can't make an off the cuff estimate. First you have to figure out roughly what's wrong, what parts costs, the time you'll spend and the risk you're taking then give a quote based on that. And very often the customer will say it's not worth it and go buy a new machine and that time is lost. And then you'll have customers who want time estimates or worse yet guarantees and you have supply chain issues you'll spend time dealing with customer complains and they might haggle or cancel their business and you might get stuck with the bill. And you will have all the ordinary business overhead of having a shop, maintaining an inventory and billing system, taxes etc. and people that don't ever come to collect or pay. And if you're shipping you will spent time wrapping and unwrapping, collecting and delivering, dealing with transport damage etc.
I have some friends that are in the construction industry, they say pretty much the same. If you take away all the overhead, preparation and cleanup and just look at the time the handyman actually does this craft the hourly rate looks bizarre. But after dealing with "everything else" it's not like they walk away with that much per hour worked. It's the cost of doing it as a business, if they were just working on their own house they could do it way, way cheaper. It's simply a matter of trust and risk management, like I rented an apartment from an ex-classmate some years ago. Even though we weren't exactly friends he'd much rather rent to me than to some stranger, simply because he knew I'd be a no fuss tenant. The money is in easy business, dealing with complex and unique situations lie half-broken machines is often unreasonably time consuming and thus expensive. Getting a "known good" one off the assembly line often wins on simplicity.