If i buy, i would pay 15 $ a month for the frogengine.com, and if it is on bloggertalk, you can ask about 35 - 40 $ a month.
Thanks a lot for your feedback. Based on that, I will sell 3 links on frogengine for $100.00 for 6 months total and 6 links on Blogger Talk, $100.00 for a total of 3 months. Those who are interested can PM me. - Mike
Textlinkads has a great tool for determining how much a link is worth (i cant link you there bc i don't have sufficient privileges). I personally think that they show you an inflated value, but it's been my experience that there are always buyers willing to pay that price if you list with them.
I have a client with a ~500 page PR5 site. Charges $25/month for site wide links. Bottom of page on all pages. Famous comedian, star of "Make Me Laugh" on ABC a few years back. If you're interested, let me know by email or PM.
From reading a lot of link sale posts I would say about $15 a month for a PR5. Of course there are lots of other factors but this seems about average.