Running a small Adwords campaign just now, and you would not believe how much the bid prices are fluctuating by - single keyword last night was £2.50 (I'm Uk) - this morning, was £1.50, now £0.25 so , of course I weighed in just now. Is this to do with traffic at the time, popularity, my ads performance or what? Any ideas - just wondering if its useful to start a campaign and watch the keyword you really want until they come down to an affordable level?
Basically I think the keyword price is varying because of bids by other persons. Basically adwords is like an auction. So the tools automatically changes the price depending upon the current bid value from other adword advertisers. Hope this helps you....
it has a lot to do with quality score adjustments as well as competition at different times of the day.