Not many professors from business schools leave academia in the US partly because in business schools the salaries are much higher compared to other fields. Of course they are still lower than in the industry. However, many b-school professors do consulting and executive education which pays really well - anywhere between 2K to 10K per day. Btw, you can look up salaries of b-school professors in state universities in most states. (This usually excludes other income though) Some of the top professors make more than a quarter million a year. The highest I know earns more than a million a year only from salary.

I know a few people who quit business schools to join industry. Their reasons were mostly personal (spouse didn't get any job or the weather was terrible). They joined different companies in the Bay area. One of them said he is very happy with the transition in terms of money and dynamism but he rarely sees his kids now!