I've got more than 20 well established pr5 sites ... and the range of their traffic, revenue (a very complicated thing for these sites) and topics vary widely as does their intrinsic value. PR is just a corner piece in a very large puzzle that is the value of a site.
If you can find folks that buy sites based on PR alone, then they're probably heading for a meltdown, because there is so much more to site value than the number a flawed algorithm assigns to them.
imho ... just a little pet peeve rant.. LOL
Vivvy