you don't say!

used either to express surprise or lack of surprise in a humorous and slightly unkind way

(表示惊讶)不会这样吧!不至于吧!(幽默且不太客气地表示并不惊讶)我就知道!

"He's lost his job."

"You don't say!"

“他丢掉了工作。”

“不会吧!/不至于吧!”

"I'm a writer."

"You don't say. What kind of book are you writing?"

“我是个作家。”

“真的吗，你在写什么样的书呢?”