i personally love vB and would recommend it to others. There are a ton of free forum software out there SMF, phpBB, etcc.. etc.. but i honestly dont mind paying full price for a piece of software if its worth it.
but as others have said look arround. There are other forum software that can compare to vb feature and popularity wise.
Webdude, tell me where in my post I mentioned the word "free."
However, I will say that for this instance, a free forum would be better. If you cannot afford vBulletin, chances are you probably don't need the support, which is what I see as the main draw to using a paid piece of software.
I also wouldn't necessarily say cPanel is cheaper outright than H-Sphere. H-Sphere is ~$4/acct with billing, whereas cPanel is $1600/server without billing. Seems to me that H-Sphere would be the better deal.
Back on topic, I personally like MyTopix. From a developer's standpoint, the entire code is object-oriented and commented, which makes it much easier to work with, at least in my opinion. Of course it may not be good for someone who needs support or wants hundreds of mods available, but is if you want a forum with clean coding.
vBulletin is also not the only paid forum. Woltlab Burning Board is only $35 and has a pretty decent community behind it.
I just wanted to bring up that vBulletin isn't the end-all of forums, and you shouldn't "break the bank" for it if you don't really need it.