AWS matched a few months later:
https://aws.amazon.com/blogs/aws/free-data-transfer-out-to-i...
I'm not trying to convince you to stay (I work for neither anymore!), just wanted to note that you can technically request a waiver. I'm not sure how this works in practice though. Like, if you want to leave Athena and move to something on-premise is that enough to have just that workload? Maybe!
Edit: I also didn't follow this at the time, but the AWS wording suggests that the "EU Data Act" is also involved.