There is a shell command that allows you to measure how fast the data goes through it, so you can measure the speed of output of commands in a pipe. So instead of:
$ somecommand | anothercommand
you can do something like:
$ somecommand | ??? | anothercommand
And throughput stats (bytes/sec) are printed to stderr, I think. But I can't for the life of me remember what that command was.