He may have done that if he hadn't already been in the middle of making his point. He wanted her to understand that if you can't afford something, getting it for free isn't right. So if he gave it to her for free, she would be happy and say "oh yes, I see your point! Thank you friendly man!" but really nothing would have been accomplished. If she's going to accept the implications of doing what's right for the sake of doing what's right, she has to accept those implications while feeling all the nasty consequences that come with it.
Of course, he slowly realizes that no matter how reasonable he is with her, she's already dead-set on maintaining her point of view. So he wraps up the conversation with some nice stories to make a point to us - the bystanding readers.