1 Lie detector tests conducted by certified professionals typically cost $200-$2,000. 2  The length of the test plays a factor in the price, with all-day tests on the high end of the range. 3  Typical two-hour, single-issue polygraph exams are generally $200-$800.ie detector tests, also called polygraph tests, are used to determine whether a person is telling the truth. According to the American Polygraph Association, research has shown standard lie detector tests are 80%-98% accurate.