Here is how they do it!
There are conservatively 500,000 Extang Tonnos on the road everyday and based on the average gas savings, we save America 60 million gallons of gas per year or approximately $100,000,000.
Studies show the average truck owner drives 18,000 miles per year. At 15 mpg that comes to 1,200 gallons of gas.
At a minimum 10% savings you would save around 120 gallons a year (and many reports show it to be more like 12%).
You can see why it would not take too many months to have your new tonneau pay for itself.
MORE INFORMATION: http://truckstuffdirect.com/extang-solid-fold-tonneau-cover/