I don't think it is worth that much. I had added my sites on Yahoo Directory and kept them there for 2 years but haven't ever seen a single referrer from Yahoo. For me, it doesn't even help you in SERP's
Please explain why you think $299 is worth paying for listing in the Yahoo directory. Does the Yahoo directory produce volume referrals or increase your PR by a factor of -- how much?
It says to do it in google's webmaster guidelines! So of course it's worth it if you are serious about search. The Yahoo directory is human edited and they want only relevant results in their directory, so what better place for google to determine what community your site belongs to than to grab it all from Yahoo! The same concept applies to DMOZ and a handful of other directories. Although a strong majority of directories are garbage some of them can be totally trusted and are great places to have links!