Planet13 - 6:55 pm on Jan 26, 2011 (gmt 0)
5) the best link buys i have ever done are the ones that generate referral traffic.
Maybe you can get better ROI by setting up an affiliate program and soliciting lots of affiliates from high traffic sites, instead of buying a link from a single high PR site.
Also, I think if you were just trying to get an idea of how much you should pay for a link, you might want to repost your question in the link development forum. You might find some people with more experience buying and selling links in that forum.
I hope this helps.