Totally deprecated Like totally.
This post is ancient, out of date and I’m not going to update it. So, why does it get so much traffic???
More info at AppEngine and Amazon EC2

If you want to be the next Facebook at some point you will have to figure out how to scale to support millions of users. Amazon EC2 has been a popular choice for adding servers as they are needed and a number of busy Web 2.0 sites use it. Google App Engine is a new option. It allows application developers a chance to use the same building blocks used by Google, but it is different. GAE developers cannot change the underlying operating system or even write to the file system except though controlled methods. On one hand it’s a limitation but on the other hand it will force you to develop apps in a Googley way that can scale to millions of users. This is a very good thing if you’re developing the next MySpace. More on this later.

In the meantime, here’s some information on the announced Google App Engine pricing as mentioned on TechCrunch. I’m at Google I/O tomorrow and the day after.

Property Google App Engine Amazon EC2
Sources:

What is it??? The App Engine service is basically access to Google application service infrastructure including Datastore API/BigTable to store stuff. You have to use Python as your development language for now. You cannot open raw sockets to other machines, although you can pull stuff into your app using URLFetch on port 80 and 443. EC2 is a virtualized server. It will run whatever you put on the server space it gives you, but you have to set-up and configure everything yourself if you don’t use prebuilt AMIs. If you want one small server or a thousand big ones, you’ll pay for what you use.
Is it reliable? Preview service for now, but it should be as reliable as Google eventually. Some notable hiccups, but yeah its as reliable as your code and the platform you choose.
Try before you buy? Yes. Free quota to get started: 500MB storage and enough CPU and bandwidth for about 5 million pageviews per month No.
Scalable? This service is all about scalability. It is highly optimized for building apps that serve millions of users. Yes, if you use conventional methods for scaling web apps, you can add more machines quickly and easily. You do have to plan for it though.
Supported languages You can choose any language you want as long as it is Python. Ha. This will change! Anything you can load on your AMI.
Authentication built-in? You can easily authenticate your users with the Users API. Anybody with a Google Account can then add your app. Not applicable really, as it depends on how you set-up your server.
UNIX skilz required? Much of the sysadmin stuff is done for you by Google. You can use prebuilt AMIs, but if you are going to be making a busy site, you better know how to tune your OS and your development stack.
Memcached? Yes. Google supports memcached. Yes, apparently this can be done by installing memcached and controlling access with iptables. See the comments. Anyone got a link?
Computation charge per CPU core-hour $0.10 – $0.12 (billed on actual cycles used by scripts) $0.10 small, $0.40 med, $0.80 large (billed as long as your instance is active)
Storage of your stuff per GB/month $0.15 – $0.18 in BigTable Depends. $0.15 in Amazon S3 (plus data and query charges) or $1.50 in Amazon SimpleDB (plus SimpleDB machine costs and data transfer costs)
Bandwidth charges (outgoing GB) $0.11 – $0.13 $0.170 – $0.100 on a scale
Bandwidth charges (incoming GB) $0.09 – $0.11 $0.100