How much are your private conversations worth to the U.S. government? Turns out, it can be a lot, depending on the technology.

In the era of intense government surveillance and secret court orders, a murky multimillion-dollar market has emerged. Paid for by U.S. tax dollars, but with little public scrutiny, surveillance fees charged in secret by technology and phone companies can vary wildly.

AT&T, for example, imposes a $325 “activation fee” for each wiretap and $10 a day to maintain it. Smaller carriers Cricket and U.S. Cellular charge only about $250 per wiretap. But snoop on a Verizon customer? That costs the government $775 for the first month and $500 each month after that, according to industry disclosures made last year to Congressman Edward Markey.

Meanwhile, e-mail records like those amassed by the National Security Agency (NSA) through a programme revealed by former NSA systems analyst Edward Snowden probably were collected for free or very cheaply. Facebook says it doesn’t charge the government for access. And while Microsoft, Yahoo and Google won’t say how much they charge, the American Civil Liberties Union (ACLU) found that e-mail records can be turned over for as little as $25.

Industry says it doesn’t profit from the hundreds of thousands of government eavesdropping requests it receives each year, and civil liberties groups want businesses to charge. They worry that government surveillance will become too cheap as companies automate their responses. As the number of law enforcement requests for data grew and carriers upgraded their technology, the cost of accommodating government surveillance requests increased. AT&T, for example, said it devotes roughly 100 employees to review each request and hand over data. Likewise, Verizon said its team of 70 employees works around the clock, seven days a week to handle the quarter-million requests it gets each year.

Companies also began to automate their systems to make it easier. The ACLU’s Christopher Soghoian found in 2009 that Sprint had created a website allowing law enforcement to track the location data of its wireless customers for only $30 a month to accommodate the approximately eight million requests it received in one year.

Most companies agree not to charge in emergency cases like tracking an abducted child. They aren’t allowed to charge for phone logs that reveal who called a line and how long they talked such as the documents the Justice Department obtained about phones at The Associated Press during a leaks investigation because that information is easily generated from automated billing systems.

Still, the fees can add up quickly. The average wiretap is estimated to cost $50,000. One narcotics case in New York in 2011 cost the government $2.9 million alone.

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