$50/yr. for Google Apps Premier Edition

That's per user. The difference between the free and paid versions, according to the official page, are:

10GB email storage (vs. 2GB)
Ad-free
99.9% uptime guarantee for email
Shared calendars
API available
24/7 assistance, including phone support

Not bad, but they need a killer app to really take-off, not just me-too apps.