Says you!

says you

That's only your opinion (and you're wrong)! Used to express disagreement with or defiance against some general statement someone has just said. A: "There's no way we'll be able to sell all of these chocolate bars." B: "Says you! I'm already about halfway through my stock." A: "No one is going to want to buy something like that." B: "Says you—I think it looks pretty interesting!"
See also: say
Farlex Dictionary of Idioms.

Says you!

Inf. That's just what you say!; You don't know what you are talking about! Fred: You are fat and ugly. Tom: Says you! Mary: People who go around correcting other people were found to be very annoying in a recent survey. Bill: Says you!
See also: Say
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

Says you!

exclam. That’s just what you say!; You don’t know what you are talking about! FRED: You are fat and ugly. TOM: Says you! MARY: People who go around correcting other people were found to be very annoying in a recent survey. BILL: Says you!
See also: Say
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • says you
  • sez
  • says who
  • Says who?
  • sez who
  • Sez who?
  • against
  • against (someone or something)
  • a difference of opinion
  • in defiance