Menachos 85a:
אמרי ליה יוחנא וממרא למשה: תבן אתה מכניס לעפריים?
Said Yochana and Mamrei to Moshe: Are you bringing straw to Afraim?! (i.e., a saturated market).
אמר להו: אמרי אינשי, למתא ירקא ירקא שקול.
He answered them: People have an expression, “Bring vegetables to a place of vegetables” (Au contraire, one brings the best product to a place where its superior quality will be appreciated).
(Find a Medrash with similar logic here.)