We're about 15:1 (Dev&QA/Dedicated DBA) 75:5

Breaking it down further (although everyone pitches in):

1 - Architect

2 - Admin/Performance DBAs

2 - BI/ETL Designers

We do train our devs and QA to handle basic admin of their own environments.

I find that the number of concurrent projects is more challenging than simple numbers. 1 DBA can easily handle a large team (25) working a single product. We see challenges with (25) if they're on multiple teams and schedules collide.