I'm currently flying ERJ145's only and making good profits, ~$500k/week per plane.
After the airport fee tweaks, margins have increased, shouldn't be that hard to run a regional airline.
Ensure you only fly shorter routes and that your planes are flying as much as possible. If you have high load factors you can increase prices until you see load factors dropping. I'm currently flying with as much as 30-40% price increase on some routes.