I run a $MM enterprise business almost entirely on GAE/python with a staff of ~40, public-facing site, etc and the monthly bill is under $1500/mon. Sure, I'd prefer lower $ and faster performance but truthfully, I'm no longer complaining: GAE/python saves me $$$ in IT staffing costs including security upgrades on dozens of packages that are either pre-integrated or I don't need at all (SQL & NoSQL databases incl multi-DC failover, memcache, reverse proxy, email hosting, auto-scaling, etc. etc.)