I think he's more concerned about the consumption of electricity to power the router, than the purchase cost of the kit. After all once you add the router to the network it's another thing always on, and yet by the sounds of things, normally there would only be one PC present on the network.
The power consumption may be low so the electricity bill cost is I doubt the issue. It's the cumulative effect of that consumption on greenhouse gasses, etc, when you start adding all the home networks together that I suspect is the concern. Very laudible really, even if the computer is hardly the most energy efficient industry to worry about.
Anyway, this is a bit
from the original thread question.