king's ransom vs treasure

king's ransom and treasure both are nouns.

Word	Noun	Adjective	Verb	Adverb
king's ransom	Yes	No	No	No
treasure	Yes	No	Yes	No

As nouns, treasure is a hypernym of king's ransom; that is, treasure is a word with a broader meaning than king's ransom:

Other hypernyms of king's ransom include hoarded wealth.

king's ransom (noun)	treasure (noun)
a very large treasure	art highly prized for its beauty or perfection
	a collection of precious things
	accumulated wealth in the form of money or jewels etc.
	any possession that is highly valued by its owner

king's ransom (verb)	treasure (verb)
	be fond of; be attached to
	hold dear