AWS Transfer Family Costs

Hi, I find that this is the second month I've been charged over $200 for AWS Transfer Family SFTP:S3. My question is what specifically contributes to that cost, and is there a way to use storage without SFTP?

My account is currently using just a few things on AWS. First, a web app on Amplify that generates images and saves them to S3. Would that contribute to that cost? Is there a better way to handle that?

The other thing that uses S3 is uploading a couple large (~2-4GB) files to S3 via the console, and then a third-part service downloading that, currently via a presigned URL. I think at one point I had looked into creating a script to upload those files automatically, but I don't know if that would have contributed to it.

I don't have (or don't believe I have) any kind of SFTP server set up. I just want to understand what falls under that higher priced SFTP service. Any guidance would be appreciated. Thank you!