 Drive 10,000 miles, though, and that same payment will cost you 18.5 cents per mile. This is one of your major fixed costs while paying off a truck loan. The difference in this example is only a fraction of a cent, which may seem like small change, but it ultimately amounts to $960 more annually on the bottom line. Because though fixed costs do not go down over time, you can reduce your cost per mile with more paid miles.