Is that 256kb, or 256KB - the difference is (almost) an order of magnitude.
If it helps, I get between 4KBs and 7KBs when publishing to/from a Windows
2003 server, and 7KBs - 14 KBs when publishing to Unix on a 512kbs DSL
connection. The speed range depends on the size and number of files being
published - small files will go more slowly than large files; each file
requires some overhead at each end in updating the meta data in the
extensions.