You can't compare the wattage on a BFL with an Avalon. An Avalon is a self-contained mining device. Add in the wattage for the laptop and the BFL is less efficient than an Avalon! ROFLMAO.
You are probably wrong in a couple of asumptions. For starters you can use something smaller than a laptop, eg. a Raspberry Pi. Secondly you only need the one to talk to the 5GHs, 25GHs, or 50Ghs products, at the high end power consumption the controlling computer becomes insignificant.
That's not what the demo showed, now was it? They showed the power draw minus the computer, which is not a fair comparison to a complete Avalon.