Congressional Oversight to Secure Transparency of Relocations Act or the COST of Relocations Act This bill requires a federal agency seeking to relocate more than 5% of its employees or more than 100 employees to conduct and make public a comprehensive cost-benefit analysis of the proposed change. Specifically, the agency must conduct such analysis and submit it to the agency's office of inspector general for review and submission to Congress. The report must include, among other things the anticipated outcomes and improvements that will result from the proposed relocation, the metrics for measuring whether the proposed relocation results in the anticipated outcomes and improvements, a timeline of past and future engagements with stakeholders regarding the proposed relocation, a comprehensive strategy for accomplishing the proposed relocation, and an assessment of the short- and long-term effects of the proposed relocation on the agency's mission.