Would you like to have a cup of tea?
Sure. Thanks!
Would you like to have a peg?
No, thanks!
When someone offers me a peg, I first deny the proposal and then say thanks. Why? Because he offered me something.
But then, there exists a response…
Thanks, but no thanks!
What's that? Is that second 'thanks' is redundant?
While I understand no thanks (it already includes thanks), I wonder what first 'thanks' is doing there?
Best Answer
I think that "Thanks, but no thanks! " means:
"Thank you for the offer, but no thanks to the offer". "No thanks" is kind of a "set phrase" I guess, so we include the thanks again even though we've already said it once at the start.
It is true that you can say "Thanks, but no", however it sounds a bit firm.
EDIT: As has been discussed in the comments, many other native speakers believe that almost the opposite is true: "Thanks, but no" sounds sincere, and "Thanks, but no thanks" sounds sarcastic. However, we all agree that it depends dramatically on the way in which it is said.