You can host your own S3 API-compatible object storage service on some EC2 instances (exercise left to the reader to figure out how to make that reliable). Zero PUT cost, higher operational overhead.

  Minio: https://github.com/minio/minio
  SeaweedFS: https://github.com/chrislusf/seaweedfs
  Ceph: https://ceph.com/en/discover/technology/