costly vs high-priced

costly and high-priced both are adjectives.

Word	Noun	Adjective	Verb	Adverb
costly	No	Yes	No	No
high-priced	No	Yes	No	No

As adjectives, costly and high-priced are synonyms defined as:

Other synonyms of costly include dear, pricey, pricy.

costly (adjective)	high-priced (adjective)
having a high price	having a high price
entailing great loss or sacrifice