If the X-Prize folk searched "atmospheric water generator", they would find multiple commercial products that run on electricity. Then, they would simply need to set up a solar panel system, and they'd be done.
I live in a desert, and have looked into getting one of these systems. The (commercial) system I'm looking at has a cost that would meet their guidelines for production and cost, provided a working life of about 20 years. That's... not unreasonable.
Why don't we all use this technology? Because I'm billed for water (in the desert, in a drought) at $0.0015 per liter. If I'm really wasting water, and I get a fine for over-use, then I'm punished with a rate of $0.0036 per liter. If the cost for atmospheric water condensing was $0.02 (the X-Prize target), it still wouldn't be cheaper than aqueducts hundreds of miles long or ocean desalination (the two sources of my water). If they're going to have a cost target, it should be a lot lower. Really, they should be looking for creative ways to scale and capitalize the existing systems. We don't need more technology here, just different financing models.