Does new line delimiter for Kinesis Firehose incur extra costs?

Hello.

As far as I can see in the document below, I don't think there is a charge for the "new line delimiter" function.
https://aws.amazon.com/firehose/pricing/?nc1=h_ls

You can enable Dynamic Partitioning to continuously group data by partitioning keys in your records (such as “customer_id”), and deliver the data grouped by the partitioning keys to corresponding Amazon S3 prefixes. With Dynamic Partitioning, you pay based on the amount of data processed through Dynamic Partitioning, and per object delivered to Amazon S3. If you use the JQ parser for Dynamic Partitioning, you pay per hour of processing for the JQ parsing.

I recommend that you open a case with AWS Support under "Account and billing" just to be safe.
Inquiries under "Account and billing" can be made free of charge.
https://docs.aws.amazon.com/awssupport/latest/user/case-management.html