This is an issue that became popular because of the date. The estimated number of clicks per day according to Google when we set up the campaign was 1.2 clicks per day.
Since we set the campaign up a day ago we have had 285 clicks, each of them has cost 4p.
The lessons here are :
1. Take the estimate of traffic as just what it says, an estimate
2. Don't accept the price guide, that too is an estimate
3. Be prepared to monitor the campaign like a hawk for the first few weeks of the campaign being live
4. Don't tell your competitors
Okay - it may not be absolutely useless. They do give an indication of popularity of one keyword over the other.