The thing about paying for this list is that you are still listed in much shorter listing and thus more viewable for that month. Consider this, you pay for the listing and your site is put into a pool of lets say 200 sites that also pay. People will search these first as they are easily seen as quality domain names, thus your exposure is greater. If not your domain is buried in a list of thousands and becomes less likely to be seen and so harder to sell even if your domain name is a great one. You might even try getting your domain listed with some of the more selective domain sellers also such as
www.greatdomains.com. You should be aware that you must submit your site for approval to these sites and they are highly selective in their domain approvals, but your domain is more easily viewable.
The $39 that sedo charges is worth the exposure if you can afford doing this for a month or two and if you sell your domain quicker than you will be glad that you used this method.
Kevin