Text Link Ads launched a Text Link Ads Calculator that tells you the value of a link on a particular Web site. The price is derived based on Alexa ranking, link popularity, site theme, numbers of links available to be sold, sitewide versus single page link and most importantly, the location of the link on the page. The thing is, when you test it out on this site, you get the following prank!
There are several other examples of funny responses, including wolf-howl.com, seomoz.org, msn.com, davidnaylor.co.uk, shoemoney.com, text-link-ads.com, webguerrilla.com, and jeremy.zawodny.com. Also if a site is like a Google.com or Yahoo.com, you get the "Priceless!" response. As an FYI - SEW Blog is worth over 6k per month for a single link. More details at the link building blog.
Forum discussion at DigitalPoint Forums.