sumptuousness vs expensiveness

sumptuousness and expensiveness both are nouns.

Word	Noun	Adjective	Verb	Adverb
sumptuousness	Yes	No	No	No
expensiveness	Yes	No	No	No

As nouns, expensiveness is a hypernym of sumptuousness; that is, expensiveness is a word with a broader meaning than sumptuousness:

sumptuousness: the quality possessed by something that is excessively expensive
expensiveness: the quality of being high-priced

sumptuousness (noun)	expensiveness (noun)
the quality possessed by something that is excessively expensive	the quality of being high-priced
wealth as evidenced by sumptuous living