I think GiggleBerries is confusing yahoo with one of the other engines. I know that you can pay for keywords in overture.com formerly goto.com, and a couple of the other pay per click engines, but yahoo is a $600 per listing for adult related sites.
Our search engine plan of attack has been to use
www.positiontech.com to get in the Inktomi engine, we then add the link to the new site from all of our pages that are already listed in google.com to get the new site spidered also. Using this method we can ramp up to around 250 - 750 hits a day within 60 days, and it only costs us $60 since we submit 5 pages for each new site. (** Note we use a program that feeds the search engines targeted doorway pages whenever they spider, and we submit 5 of these pages to get a good set of keywords and phrases).
We then use the $$'s that we make from the site to pay for the $600 yahoo listing, which is normally within the first few months. We might also kick in $79 to list it at altavista, they don't send as much traffic as yahoo, but then again they are only a 1/10th of the price
And finally we shift into maintance mode, and we allocate 15% of the sites revenue to buying traffic on overture.com, we play around with keywords and phrases, but have found that the cheaper bids don't always payoff as well as bidding more and getting listed in the top 3 spots which are seen on a much wider scale.
We are working on site 21 right now using this method, and so far it has been a very repeatable, and very profitable
I hope this helps with your own SE plan of attack.
Tim