I totally understand the need for maintaining servers! Prizes are fun too! Especially if you give away stuff like a life sized BR... Oh yeah!
ooh life size BR, i think it would be cool to have a life size halo sniper, it would probable be taller than me if i stood it up on the butt end of the rifle
although I obviously don't know how much it costs them, servers aren't cheap: Most of the problem is bandwidth. Getting a dedicated line (which you need to for a server, so it won't crap out during peak hours) isn't cheap. Sending and receiving so much data adds up to a lot of bandwidth usage. Especially when FH is linked to by other sites (and especially when bungie linked to it for the 2007 map awards), that is a LOT of data. ISPs are happy to charge you for serving all that data on a dedicated line.
The price of the server will not be released. But, I will say that the ad money is needed to pay for it. (Just be glad we don't have a donations block up.)