[Someone1234]

When your cloud provider lets a client run their own source code, how can you REALLY determine that incoming traffic is even from a crawler? Do you want them to spawn a specific instance of the app just used by Googlebot and then using a load balancer to redirect those requests to those specific instances?

The more you think about this, the more insanely complex it gets.

[skj]

Google crawlers come from well-known IPs, especially well-known to Google. Appengine requests come through reverse proxies, and there is no fundamental difficulty in not counting requests from crawlers towards the quota. That said, see my other descendant comment.