Per account.

How much do you pay your employees?

What?

I use Google Apps to host 4 email addresses for my personal domain.

Personal email Online shopping email Forums/Programming email Facebook-only email (so people can't search for me)

I use it for me. I wouldn't pay $20/month for such a service, and Google is smart for not taking free away from existing customers.

People in need of more than a few accounts would blow through the free version quickly.