netmeg - 8:42 pm on Feb 1, 2010 (gmt 0)
By the way, as an AdWords advertiser in some pretty expensive niches, I can tell you that that Keyword Tool is great for suggesting related keywords, but not so hot on suggested pricing. I *never* have to pay anywhere near what they say the going market is on my keywords - for example, I have a set of keywords that show in the neighborhood of $18 to $27 in the Keyword Tool, and I, with a QS of 10/10 am paying no more than $3, for spot 1-3 in search.
Content network campaigns are often priced below search campaigns (and the Keyword Tool, as @incrediBILL mentions, doesn't cover Content) plus you don't know if they clicked the first ad on your site or the last (even if you're using channels, that only applies to ad BLOCKS, not individual ads), at the time they clicked, the top advertisers in that niche may have exhausted their budget for the day, plus you could be smart priced - there's a number of things that could be going on.
Bottom line - don't go by the Keyword tool.