"As expected the average price for a drug test reported by the majority of respondents (67%) ranges between $20-$50. This would vary depending upon the drugs being tested, collection and shipping fees, and Medical Review Officer (MRO) services. The low end cost of $10-$20 reported by 15% of the respondents was most likely in-house instant urine tests."

Source

Fortner, Neil A.; Martin, David M.; Esen, S. Evren; and Shelton, Laura, "Employee Drug Testing: Study Shows Improved Productivity and Attendance and Decreased Workers’ Compensation and Turnover," Journal of Global Drug Policy and Practice (2011), Volume 5, Issue 4.