I asked a (yiddishe) car dealer to look out for a particular car for me. I made it clear that I'm willing to wait to get a good deal. After several months he showed me one such car and asked if I want it. The car had several faults which he said he would fix before selling the car to me. He also asked me if I was certain about taking the car as he didn't want to otherwise do the repairs. I confirmed that I wanted the car. The repairs are not yet complete. I have found that the price he wants for the car (£3200) is a lot more than what I've since found from another (non-Jewish) dealer (£2290). Also he asked for £500 to help him cover the costs of the repairs, which I gave. My shaylo is whether I may now back out of the deal (maybe to pay him something) or not.
Answer:
It is legally possible for you to back out of the deal. You have not made any legal kinyan on the car, and you have not even paid for it, so that there is no issue of a mi she-para (the punishment for backing out after payment has been made).
However, Chazal state that a person must keep his word, and the dealer, in this case, asked if you were sure, to which you replied in the affirmative. According to some authorities, backing out after giving one's word is a full prohibition, whereas others write that it is not a full prohibition, but only an action criticized by Chazal. Either way, it is certainly proper conduct to keep one's word (see Choshen Mishpat 204:4; Iggros Moshe, Choshen Mishpat 1:58).
In this case, there is room to argue that you agreed to but the car thinking that it was a good deal, and that now you have realized that it isn't a good deal. However, this reasoning is unsound, because a "good deal" is a relative idea, and the dealer probably thinks and will argue that it is a good deal. Therefore, in spite of the loss involved, you should keep your word, and you will surely gain from it in the long run!
If you do break the deal, you would nonetheless have to compensate the dealer for his expenses in repairing the car.
Best wishes and much success!