File transfer speeds fluctuate widely based on SEVERAL factors.
One of which, as HostSlim mentioned, is the speed of YOUR connection,
as well as the speed of the receiving server.
In addition, you need to find out whether your ISP or the receiving host
company uses any form of throttling. Many ISPs promote super fast upload
and download speeds, but, if you read the fine print, it's usually fastest
for the first 10 or 20 MB only, after which, the upload/download speed
slows down tremendously.
Other factors include your overall local system specs (ram, processor, etc.)
You have to remember, when uploading/download a file, the 2 systems are
writing information back and forth, so other factors come in to play as well.