As Adwords support gave an answer as a politician would (saying a lot without saying anything...) maybe some of you have a clue for this.
I tried to get a best guess for a yearly budget for a non-profit organisation.
I entered different maximal CPC values and depending on the maximal CPC I entered the cost for the very same amount of traffic was up to 6 times higher (with the same settings).
Why is the traffic estimator increasing the estimated range of the cost of a campaign? Why is it telling me that the estimated range of the cost is 6 times higher for the same traffice if I increase the maximum CPC I am willing to pay?