Damn you, I'm trying to get the cash together for one now.....let them stay rare
Copying what MJG said ^ It's probably because they're a lot rarer than the Volvo's. Been keeping my eye out for one and decent ones don't come up that often (although saying that, there were a few around in the middle of January...)
Whereas Volvos, BMWs, Sierras etc are always available