Airbyte ingests data into raw tables and applies the process of normalization if you selected it in the connection page. The normalization runs a full refresh each sync and for some destinations like Snowflake, Redshift, and BigQuery, this may incur more resource consumption and more costs. You need to pay attention to the frequency that you’re retrieving your data to avoid issues. For example, if you create a connection to sync every 5 minutes with incremental sync on, it will only retrieve new records into the raw tables, but will apply normalization to all the data in every sync! If you have tons of data, this may not be the right sync frequency for you.
There is a Github issue to implement efficient normalization while using incremental sync, which will reduce costs and resources in your destination.