Walt was on an ego trip the entire time - the money was an excuse but the feeling of being in power and in control was always the real reason for his actions. Remember that he torched some guy's car and turned down a generous job offer for personal, functionally petty reasons before he'd started cooking. You could argue that the offer was patronizing, but if his concern was really about taking care of his family instead of wanting to feel like he was the big guy in charge of things would he really have said no?