A/V + 기는(요) is used to emphatically disagree with a previous statement:
-- 이 책을 다 읽었어요?
-- Have you finished reading the book?
-- 끝나기는요? 책을 읽는 것을 시작하지 않았어요! -- Finished? I haven't started reading it!
-- 지금 너무 춥죠? -- It's really cold now, right? -- 춥기는요. 다음 달에 기온이 더 낮아질 거예요 -- Cold?! Next month the temperature will get lower.
A/V + 기는(요) can also show modesty in accepting a compliment :
-- 한국말을 잘하시네요.
-- You speak Korean really well.
-- 잘하기는요. 아직도 실수를 많이 해요. -- Well? I still make lots of mistakes.
-- 옷을 잘 입어요. -- You dress very well. -- 잘 입기는요. -- Dress well? Oh not at all... (blushing)