high life vs extravagance

high life and extravagance both are nouns.

Word	Noun	Adjective	Verb	Adverb
high life	Yes	No	No	No
extravagance	Yes	No	No	No

As nouns, high life and extravagance are synonyms defined as:

Other synonyms of high life include highlife, lavishness, prodigality.

high life (noun)	extravagance (noun)
the activity of excessive spending	the activity of excessive spending
	the trait of spending extravagantly
	the quality of exceeding the appropriate limits of decorum or probability or truth