The blowout cost last year was the Toyfair report. We ended up having bandwidth demand in the four weeks after Toyfair, than we do for an entire year running this board. I didn't expect it to get that much attention last year, and the excess usage fees were about $800 (which I only found out about when they billed me - I've never needed to monitor bandwidth usage, because we don't use much here).
That underestimation on my part isn't something I want to pass onto others, and I'm looking at better hosting options before this year's toyfair. The move will also try to incorporate some discrete advertising, as revenue to pay for this constantly growing board and community that's using it. But when you think about the standard running costs here, you have monthly hosting fees, domain name registration, business registration, plus various other expenses like competition items and postage to winners. For me, I don't think much about the cost, as I feel it is part of the bigger expense I pay for this hobby. I do it for my own fun - if other people benefit from it, then it is a bonus.