Well detailed answer @bianca_unifeye. 

@Nidhig - There is no such silverbullet that migrating the workloads to Databricks will always reduce the cost. It rather depends on multiple factors such as the job configurations, the type of clusters you used, etc. However, with our last migration from ADF to Workflow certainly simplified our job pipelines and increase the audiatability and observaability besides reducing the visible cost, more importantly operational cost.