“Sew buttons on your underwear!”
This is the correct response when someone answers with “So?”
We used to respond with “So there.” but my ex-husband taught me what they say in Wisconsin. He learned it from his Mom.
(I looked up the meaning; In the Depression people were very poor. When the elastic wore out on their underwear, they would sew a button on it and fold it over.)
This will confound any speaker and guarantee you getting in the last word.
https://lindaghill.com/2017/09/27/one-liner-wednesday-works-for-them/
monicle's chronicles 
I’ve heard that phrase before. I didn’t know it came from the depression.
I read the story of a woman that made a small fortune entering contests (I forget her name and the name of the book) and the author (her son) talked about his mother repairing her girdles. Your one-liner reminded me of that.
I know that one! Don’t remember if I heard that from my parents or another Wisconsinite, but I still say it today.