Since this is a discussion about quality, could we start with the thread title?

Please note that quality can not be cheap. It would be best in this case to use 'low' or 'poor'.
Parts can be 'cheap', but then you might consider that you got your 'money's worth.'

There are certainly going to be parts that are better than the originals and there are many that will not. Clearly this discussion is leaning toward those parts that can not match the quality of the originals. Many of these original parts may never be made the same again. Also note that as other related systems in a car age, supported items may age more rapidly after being replaced. ie: in some cases replacing everything with new may provide a longer service life. I don't recommend this as it is impractical.

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85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.