4chan spends its money on male toys, anime paraphernalia, and (sometimes) videogames, all 3 of which are already advertised on the site. The avg. age outside /b/ is probably around 20-24, so it's not like they're jobless.
actually it is around 14~24... and while the demographics would never spend money online (they do on the things you say because there is no other place to get that) they do consume lots of electronics.
i bet half of the gamers and people that influence game machine builds are on that site and would be exposed to nvidia or amd banners, were they ever convinced to build brand there...
see the conundrum? they are the tech savvy, so they will never generate CTR via banner impulse buys. and no brand would build its image on that site.
