Why pay $2.66 or anything at all for that trivial service?
You can use Google Drive or iCloud or Dropbox or ZipCloud or whatever. Upload your content and send your correspondent the download link. Simple. Post Office not needed!
Or just have your correspondent set up an FTP server, log onto it, and upload your content directly onto your correspondent's hard drive. Or you can set up an FTP server, post your content, and let your correspondent download it. More work, but Google, etc., not needed, just the internet.
All you need is an internet connection. You would not be reading this if you did not have one of those.
Why do you need the Post Office to send bits? The Post Office is about dead trees, about sending physical things, not bits.
Will you scan my Machinery Handbook for me? It is 2693 pages long and the cover measures 4.8 X 7.2 inches. You won’t be allowed to break the binding.