I have some sympathy for some in the chain but none for the manufacturer. The cost of some parts simply cannot be justified. If prices were sensible diagnosis by changeout might be acceptable but they aren't. In particular I cannot see how simple and cheap to make electronic assemblies cost several hundred pounds when cost of manufacture is in the tens or less. It is unacceptable that otherwise viable vehicles are scrapped due the cost of an ECU or similar. Despite my opinions I have yet to bear the brunt of spares prices - I have not entered a vehicle workshop (other than for MoTs) in 50+ years of vehicle ownership. But I feel for those with little option but to do so.I don't disagree about it being tough to justify fitting a part that doesn't cure the issue. But these occasions are in real terms, such a small percentage of the number of service and repairs carried out, that manufacturers don't even consider them as having a negitive impact upon their reputation.
Having worked at various stages in my career for a fleet end user, a dealer and for a manufacturer, I know how frustrating incidents like this can be. I also know that most dealers and manufacturers are open to having a sensible conversation when it does go wrong.