It may come as no surprise that some links cost more than others. This is because the higher the authority of a webpage; the more effective a link becomes and ergo more expensive. There are no real metrics for determining the authority of a webpage (Many use PageRank) as the sole determiner of a page’s authority but this is not an accurate measurement.
Many site’s that appear prominently in the search results have little to no PageRank and often above websites with considerable PageRank.
How do I check a site’s authority?
If you are looking to advertise on a website and you want to measure it’s authority for the keyword you want to target, simply do a Google search and if that website appears in the results then it’s a good indicator that the website in question has authority for that particular keyword.
Having said that, there are exceptions to this rule. The Open Directory Project (DMOZ) and the Yahoo Directory (Y! Directory) very rarely will appear in the search results but are known to be highly authoratative and powerful directories. The Yahoo Directory has a $US299 recurring annual fee as well a $299USD non-refundable express submission service*.
* The Yahoo Directory offers a Submission service that guarantees your site will be submitted, but does not guarantee inclusion or prominent rankings