The "worth" to being listed in Yahoo Directory is different for each person. If you are serious about business and website promotion then Yahoo listing is worth regardless to the page you would be placed or the PR of the page. If you are not serious or your website is an adsense based website just to make money from clicks then it is not worth. Yahoo Directory Listing is worth for me but not for every websites I own. I do submit only serious site to them.
How many other decentp PR directories could be gained for permanent inclusion, for that $299 ?? Would it be better to be linked from, say, 10 x $29 Pagerank 5 directories, or just the one Yahoo directory?
I think the following would be the the correct thing to do: Pay for the first year. Watch the ROI and traffic anf if it makes sense, renew for another year.