When you upload an image to the server it compresses the file, so it’s not raw. This is why the image size is smaller on the server.
When you download the file it should go much faster due to it needing to extract the file, and not needing to use the CPU cycles to compress it.
Your images are rather large in comparison to most images I work with 3-6 GB.
Does it go faster when pulling an image down from the server?