Two of my websites are in the Yahoo directory. One was before they started charging. The second one was added in the past year, which came as a nice surprise. I had no idea, I just noticed the clickthroughs in my stats. I've never paid.

Those used to noticably help your Google PR and placement too.... but I cannot say that the latest algorithim Google uses incorporates that anymore. Paying $600 is a lot for a listing.... I would make a list and think hard about making it a priority.

Steve