Nedarim 21A

שניהם רוצין בשלשה דינרין.

In this case, one may assume that both want to complete the deal at 3 dinars, and they did not intend to vow but only exaggerated for purposes of bargaining.

גמ׳ ארבעה נדרים התירו חכמים כו׳. אמר ליה רבי אבא בר ממל לרבי אמי: אמרת לן משמיה דרבי יהודה נשיאה: מאן תנא ארבעה נדרים ⁠— רבי יהודה היא, דאמר משום רבי טרפון: לעולם אין אחד מהן נזיר, לפי שלא ניתנה נזירות אלא להפלאה.

Talmud: The Mishnah states: The rabbis dissolved 4 types of vows. R' Abba bar Memel said to R' Ami: You said to us in the name of R' Yehuda Nesia: Who is the tanna who taught this Mishnah of 4 vows? It is the opinion of R' Yehuda, who said in the name of R' Tarfon: With regard to two people who entered into a wager, and each declared that he would become a nazirite if the other was right, then actually neither of them becomes a nazirite, because naziriteship is determined only by explicitness of intent. One cannot become a nazirite unless he vows clearly and with certitude. Here too, since the intent of the wagering parties was not actually to vow, the halakha is that the vow is invalid.

רבא אמר: אפילו תימא רבנן, מי קתני ״שניהן רצו״? ״שניהן רוצין״ קתני.

Rava said: You can even say that the Mishnah is in accordance with the Rabbis, who disagree with R' Yehuda. Does the Mishnah teach: Both wanted the price to be 3 dinars? It teaches: Both want, in the present tense, demonstrating that they would have been satisfied with that price from the outset and never intended to vow, so the vow is not binding.

אמר ליה רבינא לרב אשי: אמר לו טפי מסלע, והלה אמר בציר משקל, נדרא הוי, או זרוזין הוי?

Ravina said to Rav Ashi: If the seller said to the buyer in the form of a vow that the price must remain more than a sela, and the other declared in the form of a vow that the price must remain less than a shekel, what is the halakha? Is this a vow, where each stands firmly in his position? Or perhaps this is also merely for encouragement?