I really am clueless in regards to this stuff so just one more question. Do you reckon if Supherohype had over 1,000 forums that it could sustain itself through just ad revenue? Or would other solutions such as (voluntary) subscribtion have to be implemented?
I'm not entirely sure. There's a lot of different things going on here. I mean, for example, are you only talking about how much it would cost to run the server, or are you also including software licenses such as paying for vBulletin? [Which, for any larger site, is a must in my opinion].
Ad revenue is tricky. Some people pay you per click, other per day, others a flat rate for X time.
You can have a zillion forums, but it's pointless if you only have three active forums. And as for being able to be sustained, I am not sure, because there are a lot of variables involved. When you get a server, you've got to keep in mind how much space you're going to need, and how much traffic you're going to get. For example, a site that lets you upload up to a full gigabyte of info could go through a decent amount of traffic over the course of a month, compared to one that only lets you post, and you have to link pics and videos off site. However, if only five people post at the first site, and several thousand post on the text one daily, then the tide could shift.
Some bigger sites do make you pay for registration, or for activation of certain features [SomethingAwful comes to mind immediately]. This works when the server cost is substantially high [For example. SomethingAwful: "We charge money because it costs us $3,400 per month for bandwidth bills alone, and since we don't believe in shoving popup ads to our registered users, we try to make the money back through forum registrations."].
And again, this could be even more different depending on are you just running forums, or are you also having a real site to go along with it? Because with that stuff, you also need to consider maintainence and the like.