The cost per click is going to be set by Google/Bing/other PPC company based on how many other people are bidding on the keyword and how much they're willing to bid. While you can't necessarily change the price:

• If a keyword makes you more profit per click than it costs you to run the ad campaign, then keep running it anyway. The focus of PPC campaigns is, in general, to get a good ROI, rather than to reduce the raw cost-per-click.
• Try to find keywords that convert well that aren't as obvious. For example, "what hair clippers do barbers use" might get a decent conversion rate for people who want to buy high-end hair clippers and might have way fewer people bidding than a keyword like "buy hair clippers"; keywords with obvious buyer terms (buy, best, cheap, etcetera) tend to be targeted by many people, since they're some of the first high-converting terms that come to mind.

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