New servers cost around 7k plus software hard drives and ram. Hard drives are around a dollar per gig (you need 15k rpm drives mainly due to the raid) not to mention around 50 gigs of ram per server. Software can be also quite expensive. Hard drives will routinely fail but are easy to change (they are hot swappable), there are other points of failure but drives are the most common. For instance our server is stating predictive failure on a new drive, so far we are assuming it is the back plane which costs 214.99 for the part or we re up the Dell warranty for 1,697 per year. Servers are expensive but the costs are not incomprehensible, however that is depending on how many servers Bungie would need. Also I have no idea on the pricing for rack mount servers as I just deal with tower server (we have 3 btw).