We used to host Woot.com before they were acquired by Amazon.
During a wootOff, they'd sometimes use up to 700Mbps bandwidth. They'd have to tell us when they were doing wootOff's so we didn't mistake the spike as an incoming dDos attack.
Even at $10 per 1Mbps, which is good pricing for a multi-homed, backbone peered bgp uplink, they were spending at least $5,000 a month JUST for bandwidth. (700Mbps x $10 is $7k) Not to mention several racks of servers, and each rack had (4) 20a/120v circuits. ($300 per month each circuit). All in all I think they paid about $15,000 per month for hosting.
How much did they pay their admins? They had quite a few people working on managing the site and the infrastructure. I'm guessing at least 5 people so that's probably $25,000 a month there.
I'd wager woot.com cost at least $50,000 a month for them to operate.