How much should I charge to crochet a sweater if the yarn will be btw 30 to about 40 dollars, depending on...?

if I get a sale. The woman who asked me to do it wanted me to give her a price first, to see if she could afford it. IT was her idea, but I never did this before, so I was not sure what to charge. (I was supposed to crochet something for somebody else but they seemed to loose interest). She said if it was too much maybe I could do a scarf instead, because (understandably) she does not usually spend a tone on clothing. I don't blame her, but I just want to make sure I give her a fair price, but still make money, instead of loosing it, on making.