you must be new here

you must be new here

Used sarcastically to indicate some question or sentiment that belies someone's total ignorance of or inexperience with the way in which something works. If $500,000 per year sounds like an exorbitant amount to pay a professional football player, then you must be new here. A: "Why doesn't the film's protagonist just call the cops, instead of wandering around the woods with an axe murderer?" B: "My friend, this is a slasher flick—you must be new here."
See also: here, must, new
Farlex Dictionary of Idioms.
See also:
  • vote of confidence
  • crying towel
  • towel
  • (one) never would have guessed
  • (Is) that everything?
  • be a barrel of laughs
  • be a bundle of laughs
  • come again
  • come again?
  • a bundle of fun