If you are just throwing up a generic banner ad network, it's probably close to $.10-.25 CPM. Then multiply by how many ad units displayed per page (networks usually don't allow any more than 2-3).
So: 100,000 * .00025 = $25; x3 = $75
Very rough estimates. With a site with such a particular niche, he can probably get a higher CPM. I also count 7 ads on the home page.
Well, it's public how numbers vary so much. Mine's a niche music site so I don't think I should expect much more than what it's doing right now. I could easily improve the banners placement though, I just think it isn't worth it.