The more you want to appear for a specific keyword, the more you'll pay. If you're looking to have low cpc's, try adding more (relevant) keywords and bid low. Aim for an impression share of 10-30% on each, you'll have the lowest cpc's. Depends on the industry you're in of course: low cpc's might also indicate a low-converting keyword. Also, your competitor might have data you don't, and bid higher on specific audiences that convert better. You might miss out on those if you bid low. In the end, of course, if you keep overthinking this, you might as well quit advertising, so in short: testing, testing and testing :) test low bids, test high bids, test different keywords and invest more where it works