That depends on the scale and other particulars that are only shared/known inside the company.

In my experience, beyond a certain scale it simply doesn't make any sense to use managed services anymore. There is a high initial upfront cost in development hours and hardware that is amortized over a very long time after, and this upfront cost is partially paid for by the reduced cloud bill.

Most ETL processes should be declarative and configured in text files like you configure a CloudFormation or Terraform. Once you have that, the execution piece is relatively straightforward. I think a lot of issues and costs with ETL come from poor architecture decisions. For instance, we all made the mistake of running Extract processes with too many transformations. An extract should be an extract, transformation should come later.