According this site https://www.higheredjobs.com/salary/salaryDisplay.cfm?SurveyID=28
"Legal Professions and Studies" and "Business, Management, Marketing, and Related Support Services" are paid higher than faculty in more research oriented fields such as engineering.
It is because of:
- More demands for law and business faculty and graduates
- Higher tuition in such fields
- They bring more grants to universities
- other points?