CPC difference between traffic estimator and keyword search tool?

I look up on the cost of bose speakers and is 5.18. The I go to traffic estimator put a budget of .90 cts a max of 50 a day and that same keyword shows me an average cost of .67 53 clicks and a position of 3.2. I am very happy with all these results but not sure why the KW cost 5.18 and then on the traffic estimator I can get it for .90. I know is an average so means most ppl will pay less than 5.18 to bring the average down to .67?|||There are a lot of factors, I think. Sometimes there will be people competing for positions 1 and 2, and there will be a big price jump getting from avg. position 3 to avg. position 1. Also, your quality score is a very large factor in cost--it measures how relevant your landing page seems to be to the search. Your quality score might be much better than some of your competitors for that space. Also, the data on the keyword search tool seems to be a bit older, and averaged over a longer period. And I'm really not sure about this one, but maybe you are bidding on a general inclusion, and getting your low cost high rank placements off of longer searches, like "how to fix bose speakers underwater", while the keyword search tool was referring to an exact match of "bose speakers"?





Ahh, I wish my adsense mysteries worked in my favor like that. ;)