Paid links are a tricky area, and there are a lot of loopholes.
If a company is straight up selling you a link for money, just to manipulate Google's rankings, then that's a definite no-no.
However, if you are paying for a service Martindale-Hubbard that also happens to include a link, that could be seen as ok. Many directories also get around this by charging you a "review fee" and not guaranteeing inclusion, therefore making the payment about the service rather than the actual link.
A good rule of thumb when evaluating links is to ask yourself "Would I still want this link, even if it had no impact on Google?" if the answer is yes, then it's probably a good link. Also, evaluate the site to make sure it is high quality and in Google's graces, i.e. does it have pagerank, are its pages indexed, do they link to spammy sites or only quality ones, etc.