Aye, I agree with that whole heartedly. Its the whole timeshare market I wonder about. Basically if there is a market for this 'size' cluster for about $1,300 an hour could you build one of these and rent it out like Amazon does but more efficiently. (Sort of can you cut costs by specializing into a particularly lucrative segment of the market).
So if 100% 'occupancy' on your cluster is worth a million a month, and your cost of 'owning' a cluster of this scale is a quarter million a month, then you need to do better than 25% occupancy to break even, and anything better than that and you make money. It is an interesting financial exercise if nothing else.
The company I work for, R Systems (http://www.rsystemsinc.com/), basically does this. We own and admin several medium-sized compute clusters (200-500 node clusters) which are rented out to customers who need a lot of compute on a temporary basis.
A lot of what we do is heavily custom, and we provide a lot of support for our customers, but we still typically beat Amazon on both price and performance. EC2 might work nicely for embarrassingly parallel workloads, but they don't have Infiniband available if you're latency-bound... :)
There are a lot more to supercomputing than just having lots of machines in a cluster. Special network connection, network topology, routing techniques, specialized CPU/GPU, specialized storage, all these can make a difference.
I'm sure you can build a special "Amazon for Supercomputing" infrastructure, rent it out to clients, and beat AWS on price/performance. Just add fast network, mix of CPU/GPU, SSD, large RAM and distributed RAM disk. Have some standard network topologies for easy configuration. Have some standard cluster layouts for different computing needs. May be having the software in place for the typical supercomputing needs. The clients just need to provide the data to a cluster and the answer will be spitted out.
So if 100% 'occupancy' on your cluster is worth a million a month, and your cost of 'owning' a cluster of this scale is a quarter million a month, then you need to do better than 25% occupancy to break even, and anything better than that and you make money. It is an interesting financial exercise if nothing else.