The post doesn't mention the benchmark submitted to Top500 was with an array of ~1100 CC2 instances. (I think.)

http://www.top500.org/list/2011/11/100 says 17024 cores were present, so with 2 chips with 8 cores each that gives 1064 CC2 instances.

So that means about $2666 for an hour.

And with spot?

Here's a snapshot of the Spot Market pricing as of this morning:

http://media.amazonwebservices.com/ec2_spot_cc8_8xl_2011.png

Wonderful.

So...can we get 64bit small instances?