As far as I read about them, their model is not similar to a typical dev shop.
The main constrain that hinders the exponential growth of a dev shop is it's revenue - operational cost ratio. As your revenue increases, operational cost increases linearly. That is not something loved by VCs.
But Gigster executes projects using their freelance talent network. So they don't have to keep them in their payroll when there is no work for them.
This information is based on what I read about them. I'm not sure how smooth it will be to execute a software development with a team of freelancers though.
But if it works, then I think Gigster's model can achieve exponential growth.