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.
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.