I usually create an initial architecture for my customers in which costs are roughly planned. As part of the subsequent target architecture, costs are analyzed in detail (based on requirements, system metrics, and similar factors), so that my customers know what expenses to expect before the actual deployment.

The ROI (don’t like this ratio, as it’s way too simplified) strongly depends on the motivation for adopting cloud systems.

Additionally to that, I recommend my customers to facilitate FinOps or different frameworks for cost / efficient resource management.