There are all sorts of specifications/requirements listed (box size, ripple allowed, EMI limits) but the most interesting that is not mentioned is cost. There is no upper limit set on the BOM cost.
The contest has picked quality (the engineering requirements are not easy to hit) and schedule (there's a timeline for demoing). I bet it's expected that the cost, even if it's high right now, will only come down over time. But since there exist 0 inverters which can do this today (presumably), cost isn't a big concern if you can do something new and novel that's never been done before.