There are so many other factors involved in making a campaign profitable, click estimates are just that, estimates, to give you a guide as to how much traffic you may get.
Remember, your ad copy could be great and get you 10% clickthrough with a cheap cpc, or rubbish and get you 0.5% clickthrough with high cpc: thats where your profit or loss will happen, not because of googles click estimates.
Test test test, its the only way.