I am also considering to build this kind of site using a PR4 (real PR with page strength 2.5) domain. What price should I charge for a keyword? Please advise. Thanks!!!
If that. You would have to spin a good lie to have anyone believe that a link on there is going to help you.
Way overpriced at that. This is just like a directory, with all the value of the search listings taken out. So there's no way for a visitor to go through it and decide whether or not the link is worth their while to click. It's not as though the search engine builders won't be able to see this either, and devalue the links accordingly.