This is not just for these old cars, I think the reason for such practice is liability - e.g. someone gets only one part replaced on the suspension because he replaced all others oneself. Now if any part fails in the suspension linkage failed in service the mechanic can be dragged in as he worked last on that car.

And - bigger bills mean better revenue.

Sometimes - they just blurt out an ungodly dollar amount to shoo away the customer - old cars are a pain to service (no computer to tell where to look)

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)