Sheesh, FFS!!
He said FastEthernet *interfaces*, not network, stop twisting this around! Today equipment is typically geared toward Gbit speeds, and yeah, 97% efficiency on 100Mbit interfaces is quite doable - nowhere did he mention protocol overhead, because that is irrelevant when it comes to measing efficiency of *hardware*. You chose to use a slow protocol with lots of overhead, that your effin problem!