This is where your tracked metrics come in. Assign a monetary value to each improvement:

Reduced Cost-per-Hire: (Old CPH - New CPH) * Number of Hires
Value of Reduced Time-to-Hire: Calculate the average daily productivity loss for an open position. (Old Time-to-Hire - New Time-to-Hire) * Daily Productivity Loss * Number of Hires.
Savings from Reduced Agency Fees: (Previous Agency Spend - Current Agency Spend)
Increased Recruiter Productivity: Estimate the value of time saved per recruiter, multiplied by the number of recruiters.
Improved Candidate Quality: While difficult to put an exact number on, you can link this to reduced turnover costs, increased employee performance, and higher revenue generation from better hires.

Summing these up gives you your Total Benefits. This framework for evaluating recruitment software performance helps you quantify the impact.