Find out hidden costs when moving to AWS

Hello everyone 👋

I am opening this post to ask for some costs-related information as I would like to get an estimation of how much money I would be paying for the architecture of my service.

The architecture is quite simple. I would like to ship some data from Google Cloud infrastructure to an AWS S3 bucket and then download it in an EC2 machine to process it. This is a picture of that diagram:

With regards to costs, and as far as I have found, I would only be paying the data transfer Google Cloud to the AWS one as network egress costs and the costs related to hosting the information in S3. As stated in the "overview of data transfer costs for common architectures" and Amazon S3 pricing guide - data transfer section:

• I don't pay for data transferred from an Amazon S3 bucket to any AWS service(s) within the same AWS Region as the S3 bucket (including to a different account in the same AWS Region) if I use an Internet Gateway to access that data.
• I don't pay for data transferred in from the internet.

Am I right? Am I missing anything in this diagram (sorry for the networking abstraction I'm making in the diagram above. As stated in the paragraph above, I'd be accessing the S3 bucket by using an Internet Gateway, both EC2/S3 running in the same region).

Thanks lots in advance!