$9 is for an always-on instance. It includes no CPU or bandwidth.

AppEngine pricing is quite complex. You need to look at the (very generous) free quotes first (http://code.google.com/appengine/docs/quotas.html#Resources), and then look at the pricing (http://code.google.com/appengine/docs/billing.html#Billable_...)

Unless you have a very CPU-heavy application it's unlikely AppEngine will ever cost more than Heroku. 8 times at much seems a lot, but 5 times as much wouldn't surprise me.

Heroku is selling a lot more than Google. With Heroku there are few constraints on your app other than Ruby. You can do very traditional web development (SQL among other things) and there are a lot of conveniences available for you. You should be able to build your app faster and launch 1 instance for $0, and then pay Heroku when it needs to scale. Google will force you to build in a more cumbersome manner, but it will scale much better so you won't have to pay them as much. You are always going to pay more for something like Heroku that is very much optimizing developer time.

I think Heroku's pricing contains both the RAM and CPU cost for the instances. The Google price only includes the RAM cost of the servers, the CPU is still charged per request.

Thanks to all three of you for the answers-I didn't realize AppEngine's pricing model unbundled warmed-up app instances resident in RAM from CPU time and bandwidth, which makes their offering not directly comparable to Heroku.