How much should a business invest in replacing outdated internal software?

For companies in finance, an outdated internal system can become a real operational problem. Reporting may take longer, teams might depend on spreadsheets, and integrating new tools can be difficult.

But replacing a system that still works also comes with costs, risks, and employee training requirements.

When evaluating legacy modernization services, what should a business consider beyond the initial project cost? For example, should the decision focus on staff productivity, operational risk, maintenance expenses, or the potential return on investment?

I am curious how finance professionals and business leaders evaluate these projects and determine whether modernization is worth the investment.