There is a difference of opinion regarding the definition of a “mistaken” halitza. According to Reish Lakish, it is when the yavam is told that the halitza ceremony will make her his wife. Rabbi Yohanan disagrees, arguing that both the yavam and the yevama must understand the implications of the halitza in order for it to be valid. He explains the case to be when the yavam is told that if he participates in the halitza, he will be paid 200 zuz (i.e. a large sum of money).
In such a case, would the money need to be paid?
The Gemara relates that such a case came before Abaye, when the yavam to whom Rav Pappa’s relative fell was an inappropriate match for her. Abaye wanted to tell him that the act of halitza would complete the yibum but Rav Pappa – concerned with Rabbi Yohanan’s ruling – suggested instead that he be offered 200 zuz to participate. After the halitza was complete, Rav Pappa refused to pay, bringing a baraita that ruled in the case of a person who was escaping from prison (we are assuming that he was imprisoned unfairly) who offered a large sum of money to the captain of a ferry in order to complete his escape, that he can pay him the regular fare.
The rishonim offer several explanations for this ruling. Some say that it was the circumstances – that the escapee had no other recourse – so we accept his argument that he did not truly mean to commit himself to the payment. Others say that in such a case the captain of the ferry was obligated to assist the man who was escaping, and he cannot profit from the fulfillment of a mitzva that he was obligated to do. The Ramban points out that this argument may not apply to the case of halitza, but others argue that halitza, too, is considered a mitzva that the yavam should not benefit from.
The Shulhan Aruk rules (Ezen ha-Ezer 169:44) that although the halitza is valid even if the yavam was tricked, if money had been promised, it should be paid. Nevertheless, in a case where the court rules that the yavam should participate in halitza, she does not owe him anything.