From what I have read from people like matt from google it does seem that a yahoo directory listing does count. There is also reason to believe that yahoo may 1 day growth to become larger because of their relationship with companies like alibaba. That said I think a $300 yahoo listings would only be a small part of a marketing or search engine optimization effort.
It is important because; 1. It helps index your website. 2. To increase your site visibility online. 3. Get index in major search engine. 4. Get listed in such category of your targeted niche. But due to Panda update, directory submission did not carry that much weight in SEO but still it helps.