In our use case for Airbyte we have multiple sources streaming data to one destination. For example, if I want to ingest Google Sheets data and Salesforce data to a custom api, would I have to pay to stream ALL of that data to the custom api or only the Salesforce data? (Salesforce requires OAuth which appears to be an Airbyte Cloud feature).

I didn’t understand well your question. You want to land Google Sheets and Salesforce to a Custom API, like reverse ETL?

We are looking to take the ELT approach by dumping all of our data into a data lake before performing transformations on it.

We hace the same use case ✅