I'm running a very rough lightweight Wordpress install at http://tbrander1.appspot.com I get at best a few hits a day.
My cloud SQL instance seems to be getting treated as running 24x7 useage (d0 instance) or $10+ per month even though it is set to per use.. What gives??.. is Wordpress itself keeping it active? I have batcache and the GAE plug-in installed which is supposed to minimize any SQL hits...
Is there something I can do to get the charges ie get it running per use?
Seems this will be a Barrier/issue for many WP users if they try using GAE
It is likely that you have a scheduled task to run the wp-cron.php endpoint. The default for this is every 2 hours. This likely means you are starting your Cloud SQL database qyite frequently. Please bear in mind usage is billed by hour, so if your instance is used at all in a given hour then the whole hour is charged for.
If your app has very little usage try reducing or removing the cron frequency.