"From July through October in Florida — the four months when testing took place before Judge Scriven’s order —
2.6 percent of the state’s cash assistance applicants failed the drug test, or 108 of 4,086, according to the figures from the state obtained by the group. The most common reason was
marijuana use. An additional 40 people canceled the tests without taking them.
Because the Florida law requires that applicants who pass the test be reimbursed for the cost, an average of $30, the cost to the state was $118,140.
This is more than would have been paid out in benefits to the people who failed the test, Mr. Newton said.
As a result,
the testing cost the government an extra $45,780, he said. And the testing did not have the effect some predicted. An internal document about Temporary Assistance for Needy Families, or TANF, caseloads stated that the drug testing policy, at least from July through September, did not lead to fewer cases. "
This is from:
http://www.nytimes.com/2012/04/18/us/no-savings-found-in-florida-welfare-drug-tests.html?_r=0 but you can do a simple google search to find a ton of references.