I think owning the equipment is a part of his costs. Small stuff is much cheaper to run than big stuff, since economy of scale doesn't work the same way from cloud computing and such. I used to have a site hosted for like $50 a year, and the bandwidth required was small but "unlimited". Once you get bigger, that cost doesn't scale linearly. Also Poast isn't 100 people. I think it's several thousand active per month. Not sure on specifics though.