five dollar story
Starting to tell a story, then realizing it has no point or punchline and the only way to save it is to add "and then I found five dollars."
John: A man told me to have a nice day.
Mark: That's it?
John: Yep!
Mark: ... wow, that's a five dollar story.
Mark: That's it?
John: Yep!
Mark: ... wow, that's a five dollar story.