I help manage a small (5-15 employees), custom software development shop. We're hired by various clients to produce web or mobile-based applications. We make everything from pretty simple $10k e-commerce websites to very complex applications that might cost $100k over the course of several months. Our clients are generally start-ups, but we also occasionally work with more established companies (including the federal government).

I'm just curious what kind of profit margin would be typical for a business fitting this profile?