לזכות אבי מורי ואמי מורתי שיחיו
The מהר"י כולי klerred the following safek: What is the halacha if a man is מקדש a woman with an אתרוג that is not otherwise worth a פרוטה but is kosher and therefore people are willing to pay a פרוטה for it. Is she מקודשת?
The Yad Hamelech [grandson of the Noda Bi-yehuda] says that she is not. His proof is from the Rambam who says that one can only be a זקן ממרא if he argues with the Beis Din on a matter of kares but if it is a non-kares halacha then he is not a זקן ממרא. The Rambam gives an example: Lulav. If he argues about the kashrus of a Lulav he is cool. Well - not cool [don't give him ששי], but not a זקן ממרא.
Says the Yad Hamelech: If one can be מקדש a woman with an אתרוג that is worth less than a שוה פרוטה because the mitzva raises the price - then there IS a scenario where a psak about a Lulav [or אתרוג] will have halachic ramifications! A man was מקדש a woman with an אתרוג worth less than a שוה פרוטה, the Beis Din ruled the אתרוג kosher and the זקן ממרא said that it is pasul. If they listen to him and render her not married and then another man has relations with her, they will be liable to כרת because she is an אשת איש. So it MUST BE that the psak of kosher will still not make the אתרוג valid for קידושין.
[One could argue balebatish that the Rambam was referring to the actual mitzva of אתרוג which is not related to a כרת and wasn't at all thinking about this very rare scenario - but we won't go there...].
The Heilige Imrei Noam of Djikov [בתשובותיו ח"א סי מ"א] argued that this is not a proof. The מהר"י כולי was not talking about the value of the אתרוג to the woman because she doesn't have to take אתרוג anyway - it is a מצות עשה שהזמן גרמא. He was talking about the value of the אתרוג in the Arba Minnim market - namely to the "oilam". If so, their argument will not have כרת ramifications at all. Let's say the זקן ממרא said kosher and the Beis Din said pasul, let's go to the market and see who people follow, what the "oilam" is saying. If they follow the זקן ממרא then EVEN THE BEIS DIN WILL AGREE that she is מקודשת [if the kashrus inflates the price to a פרוטה] because that is what people are paying. So the question will not impact a question relating to a חיוב כרת.