Bandwidth monitoring and throttling way off?

[alleus]

I'm having some major issues with the readouts from the bandwidth
monitor and throttling when uploading files with ASIHTTPRequest. I
know it's a rough estimate, but for me on OS X it's kinda way off
track.

Using the sample application modified to POST a 1 GB file to my own
server, I'm getting the following results. I'm measuring quick and
dirty with Activity Monitor and iStatPro:

Without throttle, ASIHTTPRequest reports about 4 MB/s
http://dump.1g.se/upload/XIwu.png

Both Activity Monitor measures an average a bit under 1.5 MB/s
http://dump.1g.se/upload/el2y.png
http://dump.1g.se/upload/tzLa.png

The same is observed when throttling the bandwidth. In the following
scenario, I've set the maxBandwidthPerSecond to 1048576:

With throttle, ASIHTTPRequest reports about 1.2 MB/s (close enough to
the wanted 1 MB/s)
http://dump.1g.se/upload/Dkrc.png

But when measuring the actual throughput, it's more like 0.5 MB/s
http://dump.1g.se/upload/5zGR.png
http://dump.1g.se/upload/N5Hg.png

Anyone have any thoughts? :-)