Traffice cons on AWS

In general, data transfer between Amazon EC2 instances and Amazon S3 within the same AWS Region is not subject to data transfer fees.

So therefore, in your scenario where the EC2 instance and S3 bucket are in the same region and you are not using any endpoint, there will be no data transfer costs for traffic between the two services.

Also it is important to note that other factors such as data transfer between other AWS regions, the use of AWS PrivateLink, or data transfer out of AWS may incur data transfer fees. You can check the AWS documentation for more information on data transfer pricing.