Oh no, I think this is one of my major failure in my 4 years as web administrator.
I don't know about paid directory, but unlike paid backlink from articles in some SEO services, it only gives you N/A or 0 PR links.
If not, maybe a NoFollow links from PR1~4 site.
So, in your opinion, this is bad SEO practice or not?
If it is bad, why these directories are still placed in top of search engine?