Scam, scam, scam.
Legitimate PR6+ pages are not going to be selling links. They don't have to. (Not to mention that the whole idea behind this is based on the almost entirely worthless toolbar PR, not the real PR that Google actually uses for rankings, so the entire premise is bogus from the start.) Did I remember to say: "scam"?
Beyond that, do you seriously think the folks at Google aren't smart enough to monitor these listings and figure out who the sellers are? Really? Googlers are some of the smartest people on the planet, and -- let's face it -- the folks selling these links are generally not exactly MIT scholars. The guy who empties the wastebaskets at Google could out-think these bozos with one frontal lobe tied behind his back.
We already know Google doesn't like paid links being used to try to trick them into giving a page higher rankings than what it naturally deserves. Given that, and understanding that it's trivially easy for them to figure out who's selling the links... what do you think would be the ultimate result of purchasing large quantities of these bogus links?
Save your money. If you're going to spend it, put it toward some marketing activity that will actually get you good results.