I think you also use more robust components than the manufacturer where practical. I know my EB832 is great now with the work you did to it.You have a valid point. I would also add that companies that make and sell electronics don't really want to be in the repair business. They have to because customers expect proper product support, which includes both warranty and out of warranty repair services. Otherwise, their real cash cow is selling the product itself, which has much higher profit margins than the repair. Notice that car manufacturers don't do car repairs themselves for example. Apple, Dell and Lenovo contract out their repair services to a third party in TX, etc.
That's why their repair costs are so high. First, they are not set up to do the repairs at scale. Second, they are not particularly focused or motivated on making it profitable by lowering costs. And why should they? They would much rather sell you a new product than keep repairing the old one. Customers come to them by default because it's their product that failed. They can command any repair costs as they want to motivate buying new gear anyway.
All of this, while the manufacturer has no R&D costs related to the repairs themselves. They already have all of the schematics, firmware, testing/diagnostics processes and the existing parts supply chain. Most of what I had to develop from scratch.
Yes, I do this mostly because I enjoy doing it, to keep my skills sharp and get a satisfaction from helping fellow reefers and keeping expensive hardware out of landfills. But I do run it as a business, pay taxes on everything and keep it profitable even at the rate that I charge. I still have to charge for it because of my own expenses in time, parts, tools, supplies, etc. And the end cost is still lower than what the manufacturer charges. Because once you've invested in setting it up and learning the hardware, the actual repair labor is very reasonable.