The ACLU's position can be found with a google of

aclu drug testing welfare


"Another way to measure the cost is by counting what it costs to "catch" each drug user. Drug testing is not used by many private employers because of the exorbitant cost of catching each person who tests positive. One electronics manufacturer, for example, estimated that the cost of finding each person who tested positive was $20,000, since after testing 10,000 employees, only 49 tested positive. A congressional committee also estimated that the cost of each positive drug test of government employees was $77,000, because the positive rate was only 0.5%.[9]"


It will certainly enrich companies that do those tests.