sftp transfer with Nautilus slow

[Rashkae]

Here's a phenomenon I've observed in all Ubuntu releases starting with
Gutsy, and I've never been able to figure out an explanation.  Can
somone explain to me why transferring a file over sftp protocal with
Nautilus only works half as fast as using command line sftp client or
filezilla?

I've noticed this both when transferring files from a distant server
over internet or a server the next room over on Fast Ethernet Lan.  If I
use sftp over command line or Filezilla, the network bandwidth used and
file transfer speeds are almost double.  I don't think it's just a
matter of data compression on transfer, since in that case, the network
bandwidth on the Fast Ethernet should be the same.