I also ran a Minecraft mods site for awhile with my son and at its top it made $9k/mo with about 130k unique visitor per month.
More tech content sites or other more general sites I have ran haven't gotten anywhere close to those #'s.
Games and entertainment content geared towards youth do well.
Ad placement also makes a difference. 1 well placed in-content ad can make you a lot more than 3 ads. That one well placed in-content ad can generate a higher CTR and CPC vs. if you place 3 ads. When you place multiple ads, the CTR on all of them even the well placed in-content ad is much lower as well the the CPC. I have tested this extensively.