Learn English – What’s the difference between retrospect and hindsight

@Manoochehr doesn't quite catch the meaning of sardonic. It means "grimly mocking or cynical." My Webster's gives its origin as

mid 17th cent.: from French sardonique, earlier sardonien, via Latin from Greek sardonios ‘of Sardinia,’ alteration of sardanios, used by Homer to describe bitter or scornful laughter.

It really doesn't carry the connotation of superiority or low opinion all by itself, although such feelings may accompany it.

Sardonic is in fact distinct from sarcastic but not by much, and many people use the two as if they are interchangeable, which, strictly speaking, they are not. Sardonic is more extreme and negative, and one can be sarcastic without being sardonic, and vice-versa.

Overrated means that people hold it in higher esteem than they ought to. Overrated implies that people have a (too) high opinion.

Overvalued means that people place too high a monetary value on the thing in question. They may over value it because they overrate it, but the converse is not necessarily true.

In the case of the expression "overrated and overvalued" I suspect that there is a possiblity that it is being used for emphasis, but one would have to see it in context to see whether a literal interpretation is apt or whether it should be taken more figuratively.