The feedback we've been getting from employers is that they're much more comfortable paying on an hourly basis. They're worried about a team abandoning a project half way through, etc.

We're exploring different ways to charge for projects as we move forward.

+1 to the previous comment: time is an illusion, billable hours doubly so.

You know what would be great? A trusted-third-party for judging whether a project meets its requirement milestones, and payments escrow to make sure that the money is actually there when it does ...

That's interesting. Isn't one of your primary benefits (from the employer point of view) the fact that you are a premium supplier of great talent? "Great talent" including "reliable"? If not, what separates you from any other freelancer website?

Yes, and that's the primary reason we chose startups as a source of talent. They're a highly skilled, self-sufficient "swat team" that already have proven team fit.

Nonetheless, renting a startup or (team for that matter) is still a new concept for employers and they are used to paying an hourly rate for consulting gigs. If we start to see way more demand for flat-rate project from startups, we'll move in that direction.