Probably not unless you already have good amount of targetted traffic and/or feel your forum will offer something the others aren't.
Biggest cost of running a forum is time and hassle ... dealing with problem users, spammers, control freaks, recruiting mods, etc.
Add on top of that the costs of hosting, if planning to run a vBulletin forum, which uses a lot of server resources and requires a lot of maintenance to keep updated and secure...
And even that's no gurantee - many vBulletin forum operators running the latest version have been forced to turn new registrations off or spend a lot of time reviewing each one - see details at vBulletin support forum. And there are more threads about the issue on other sites.
http://www.vbulletin.com/forum/showthread.php?p=1631469
Bottom line is unless your proposed forums are going to offer something substantially different than the current ones, it's likely not worth the bother; ad click-through rates on forums is the pits.
Perhaps consider a blog that allows some limited user interaction as an alternative.
Ron