cost increase vs increment

cost increase and increment both are nouns.

Word	Noun	Adjective	Verb	Adverb
cost increase	Yes	No	No	No
increment	Yes	No	No	No

As nouns, increment is a hypernym of cost increase; that is, increment is a word with a broader meaning than cost increase:

Other hypernyms of cost increase include increase.

cost increase (noun)	increment (noun)
an increase in cost	the amount by which something increases
	a process of becoming larger or longer or more numerous or more important