This is rather interesting to see. Someone already put up a set of live charts keeping track of the AWS compute instances.

http://cloudexchange.org

What's interesting to me is that the same resource can have different prices in different regions (obvious, but interesting) and that in many cases (if not all) the costs are substantially below the retail rate for the same instance.

For example:

us-east-1, c1.xlarge, $0.25 / hour. The retail for that is $0.68 per hour. Nice discount.

Now, for me, I just wonder when this page:
http://aws.amazon.com/ec2/#pricing

Will just become dynamic across the board. The prices there just equaling the spot price. What you pay for the duration you use the resource is the spot price. If they did this they could just move to that model across the board. No reserved instances. No fixed pricing. Just the market with price changing relative to supply and demand. Seems like that would want to do this in time perhaps.

Very interesting. If it was pure spot pricing then, in the event capacity became scarce in the context of demand then more money would flow to AWS as prices rise to help expand capacity.

At the moment a us-east-1, m1.small is $0.026 / hr. This is still more that the $0.015 cost of a similar device in the Rackspace cloud. So, to do a small video encoding job I'd still use Rackspace. But, that can change pretty fast perhaps.

The one thing this spot pricing doesn't take into consideration is actual CPU resources available relative to price.

There was an analysis, I'm searching for the link will add in the comments if I find it, recently comparing different cloud servcies, their cost, and the amount of vCPU you get. For example, if I say that the us-east-1 m1.small is $0.026 and the Rackspace equivalent is $0.015. But, I get 4 vCPU's at Rackspace and only 1 vCPU at Amazon, then in reality Amazon is still far more expensive than Rackspace above and beyond the spot pricing vs. fixed pricing if you measure based on CPU Availability per dollar.

This is not a new problem. It's one that is often quite overlooked when comparing the value of one cloud vs. another cloud.