You can buy a whole lot of gas for $10k. So if you get the Yaris (which gets very good mileage), you'd save $10k (easily) over the Prius. I'd say the Yaris makes quite a statement about buying reasonably-priced, efficient cars.

If you are stuck on a hybrid, I hear the Honda Element (new one) is lower-priced than the Prius.

Best of luck in your search.