More than likely they have a good deal on bandwdith, assume they use 500Mbps a month, a traceroute from seattle shows they're using at least savvis as one provider. We can safely say they're probably paying no more than $18.00USD per month per Mbps. These are prices a small time carrier might get, they may be paying more and who knows how many other providers they're paying for or if they just buy a blend from their colo center.
Lets put that price at: $9000/month so far
Then you factor in the floor usage, normally you can get a full rack for about 2000 with 40a. I'm willing to bet they use at least 60a per rack, add in another 500. Plus they say they have a cage, they charge extra per square foot, a guess would put the cage at an extra 1000 per month.
So I'd say about 3 racks with a cage would cost around: $8500/month
So far the total is about $17,500.
Now if they staffed their own people and didn't have any outside monitoring or anything of that nature that might be the total cost. In reality they probably have a contract with their provider for one site maintenance, 24/7 on site support, hardware replacement and the likes.
At my current place of employ we pay 30,000/mo a month for that kind of service, I think we're a bit above what one would normally pay but we have a pretty high up time SLA.
Add another 10,000 a month for maintenance/support/supply contracts.
Grand total I'd say is about $27,000/month USD. It might be higher or lower depending on their deal with their providers but normally for a standard colo deal it's around that price.
I've seen sites pay out well above that (100,000+) for colocation and have an awesome return.