I once would like to make our site listed on Yahoo directory, I gave up when I saw the price. I think it's expensive for only one link. Few months ago, I start to think that it may not be so expensive after I bought some text-links from text-link-ads .com. I only bought about 25 website text links, it spent me $100 just for one month after discount.
You really have to weigh your other options. If you are like me and need to be next to your top competitors, then the money is worth it, but if you just want a good backlink, then go somewhere else and get many more for the same price.
I might not renew my Yahoo Dir link. Too expensive for a PR2 nofollow that only brings in 1-2 hits per week.
I have read quite a bit of negative things about the yahoo paid directory, personally I think it's overpriced $300 is too much, it's not worth it.
Please confirm the category where your Yahoo listing is. Yahoo directory listings aren't 'nofollow' AFAIK, or as far as I can see. Perhaps it is limited to categories where spamming is rife?