It's about materials costs. If you had a $2 stamping (cost) and needed it on 500,000 cars that' a $1M hit for those. Not to mention production steps, and replacement peices made for repairs.
I buy that to a point ...that has been the rational for many class action law suits against the car companies..
I go back to a comparison I have used earlier...the "actual" cost to produce a Pinto and a Lincoln Continental mark 4 was minimal...but the profit margin was very different..