Sure, the point is that - like with mechanics - you are not really-really assured that the official dealer personnel is actually "good", meaning that they follo

Sure, the point is that - like with mechanics - you are not really-really assured that the official dealer personnel is actually "good", meaning that they follow an "official" book where there is written something like "if there is defect A, change whole sub-assembly B" (and they BTW know perefectly the procedure needed to replace sub-assembly B with a new one). The issue is when "sub-assembly B" costs hundreds or thousands and the actual "defect A" is due to a loose connector or a cold solder (or whatever else easily repairable), the dealer will go by the book, an independent mechanic (if he/she is actually "good") will fix it for a few bucks. Compare with the re-known cases of motherboards replaced because a connector pin was bent or similar, there are quite a few related videos by Louis Rossmann.