Because of how broad match keywords work within AdWords, inexpensive long-tail keywords don’t really exist. You could have a keyword like “customizable hosted voip chicago il” but there are a couple reasons why this wouldn’t do you much good.
1. Many advertisers are still going to be bidding on “hosted voip” which will trigger ads for the longer search query. That means the bidding war is still going to be based on the bid amounts for the shorter keyword that everyone is bidding on.
2. Most long-tail keywords don’t have enough search volume to even allow for bidding. If a keyword receives fewer than ten searches per month, it is considered “low volume” and Google does not allow you to bid on it individually (you can add it to your keyword list but it won’t get any impressions). The only way to capture traffic from low volume keywords is to bid on shorter keywords or broad match keywords that will trigger ads for the longer search queries.
To clarify, I do include long-tail keywords when building campaigns. But it’s not because they are going to magically cost less money than shorter keywords. It’s because adding more keywords allows for better fine-tuning of the bid amounts.
Long-tail keywords are more of an SEO thing. In AdWords, every imaginable keyword pretty much gets matched to a broader keyword by Google’s algorithms. An effective AdWords campaign must be able to profitably attract quality traffic from popular search terms.