[MezzoDelCammin]

Not even that. I think I had mine for under 150 (on some sale). Also, there are a few cheaper alternatives, but some tests have shown them to be less reliable (either false positives, or worse - false "all clear").

There's one feature they all miss. They only measure relative velocity to You. That's definitely better than nothing, but in my experience the most dangerous drivers aren't necessarily the fastest ones, but those who pass too closely. So, something like "angle of approach" measurement would be a feature I'd personally be willing to switch my Varia for something else.