The MOST important element(s) to consider when developing a business case for a project is the:

ISACA CISM Exam syllabus in brief:

Information Security Governance    
A. Enterprise Governance
B. Information Security Strategy

Information Security Risk Management    
A. Information Security Risk Assessment
B. Information Security Risk Response

Information Security Program    
A. Information Security Program Development
B. Information Security Program Management

Incident Management    
A. Incident Management Readiness
B. Incident Management Operations