They're only all over the place now because you want one. I keep seeing Cobalt SS' (mostly the unboosted ones) all over the fucking place, but never noticed them until I got mine.
Anyway.... XB's aren't a very common bike, like a Ninja, but they're not something I would call rare either. As many of them as they made, with as many different variants as there were, the most expensive one will be like 6k. And that's with really low mileage and a bunch of good quality aftermarket parts.