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How much does it cost to hack into an iPhone? Not as much as we thought.

The FBI paid less the $1 million to hack into the iPhone 5C of one of the San Bernardino shooters, Reuters reported Friday, a figure lower than some observers had previously estimated.

FBI Director James Comey said last week the government had spent more money than he was set to make over the remainder of his tenure running the bureau. This was calculated to be $1.3 million.

The software mechanism purchased by the FBI from an undisclosed security company can also be used by the government to unlock other iPhone 5C models running the latest Apple software, even though the FBI doesn't understand how it works, sources cited by Reuters said.

The FBI declined to comment beyond what it has already said in public statements, but directed CNET to a page titled "Going Dark Issue" about intercepting communications.

The agency bought the mechanism after Apple refused to create a backdoor through its encrypted software, in spite of a court order demanding it do so.

Apple objected to the government's request, saying it was impossible to break its own encryption and creating a workaround would compromise the security of all iPhones. The company's transparency report, released earlier this week, shows it complied with around 80 percent of requests made by the US government in the second half of last year.

The tech industry rallied around Apple, lending support as it prepared to battle the FBI in court. But the government dropped the case after finding the alternative means to crack the phone's security.

Comey might know that the hack was pricey, but the sources cited by Reuters say he doesn't know which company supplied the technology, in spite of his seniority. Previous reports suggested an Israeli security firm was behind the hack.

The mechanism was purchased with a one-off payment and can be used again.

The contents of the iPhone, which belonged to San Bernardino shooter Syed Rizwan Farook, are still being examined, but early investigations aren't thought to have produced any noteworthy discoveries. In particular, the FBI hopes to discover whether Farook and his wife, Tashfeen Malik, had co-conspirators.

Update 8:27 am PT: Added the FBI's response.