I saw a video somewhere where they were opening up their cages at a datacenter (can't remember the exact one) and were showing their apple servers (quad xeons). Each box is about $5000+ depending on specs and I know they have a fail-over cluster system. You'll be looking at about $250,000 (or more) for 50 of these boxes not including the cage rent, system admins, cluster system, firewall, switch, the racks, and gigabit cables (assuming their using gigabit connections). Your looking at the far least 2 GBPS connection which would equal about 6480000GB bandwidth /mo. Assuming their using cheap bandwidth their monthly price for an unmetered line would be $30,000/mo - not including if their datacenter charges electricity fees which wouldn't be too bad. Then they have to pay system admins (and believe me they are not cheap) to work full time for them.
I really doubt their paying $2 million/mo as most "normal" size data centers don't even get close to that. My estimates are at bare minimum (50 servers is very low, I would not be surprised if they had over 1000).
Just my 2 cents.