If you had followed in your Prius behind the "top" Mirage in each of these contests, I'm sure you would have beaten their results.
In my experience with Toyota hybrids, the key to stellar mileage is causing the engine to shut down at every possible opportunity -- ie. completely lifting off the accelerator to kill the engine for long engine-off coasts while approaching stops/turns/downhills, etc. That, and minimizing brake usage.
I took a friend out in his Lexus hybrid a few months back and we saw 70+ MPG / 3.4 L/100 km in sub/urban driving. "Real world?" Probably not for most people, but not stupid slow or holding up other drivers, either (though it wasn't busy).