Uploading millions of files to S3

For now I am trying to use Java SDK upload a lot of small files to S3. About 8 million a month. I know there is fee for posting. $0.005 per 1000 put/post requests, and the inbound transfer is free. Will there be any outbound transfer for uploading that many files? I was watching the network activity when I tried to upload objects. I found there is about 25 KB response every time I upload one object.

So, will the 25 KB be considered as the outbound transfer? Since I am going to add millions of files, it will be huge if considered.