That is a loaded question.
Cleaning of a rare coin is more forgiving than cleaning of a common coin.
Rariety includes both population and grading census.
The decrease in value of a MS grade 1921 5 CENT coin which has been cleaned
is negligible. The cleaning did not affect the rariety.
Whereas common dates of a comparable grade of the same series which have been
cleaned will take a more substantial hit as many better ensamples are affordable
in the marketplace.
doug