This isn't what you think it is.
This is a specific device for a specific job. There are are a bunch of people who would be ripe for the picking in designing the project. It is very much attainable with today's tech, it is within the "perceived limits of engineering", even if the the environmental specifications are a bit vague.
But what if you're not willing to pay what it would normally cost to get the project done? You hold a competition of course!
Why aren't any of those existing engineers entering? Because they're not stupid. Why are none of the established design firms (engineers, project managers, admin staff etc) entering? Because, again, they're not stupid. If they were commissioned through regular means to do the job, they'd be earning a whole lot more than whatever the "up to one million" means.
The fact is, Google is hoping to do it on the cheap, and is too cheap to say.