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it all depends how competitive your category is in Yahoo, plus level of need for your product or service.
the paid submissions to Yahoo & LS are well worth it, and you probably will find that it will be with under 1000 visitors per day (even highly targeted) they do pay for themselves rather quickly, in my experience. all depends on the product.
It all depends on the title and description you receive from the editors. It also depends on what kind of product you have, and of course, how many people are looking for it. I would use something like the Goto.com search suggestion tool [inventory.goto.com...] get a very rough idea of how many people are searching for what you offer. 1000 good hits a day is tough, most sites would not get that from Yahoo unless you get a fantastic listing.
Using a seo firm with a good Yahoo track record can be very rewarding. Hard to determine how much help they have been in creating your description, but the difference between a good description and a bad one can be night and day. It may very well be worth it to you.