Most systems are implemented with direct conversion because it is the cheapest.

Direct conversion, also known as the "big bang" approach, involves a complete and immediate switch from the old system to the new one. While it might seem cost-effective in theory, it can be risky and expensive due to the potential for significant disruptions and the need for extensive support and troubleshooting during the transition. Other methods, such as parallel running, phased implementation, or pilot studies, might incur higher upfront costs but can offer a smoother transition and potentially lower overall costs by mitigating risks.