The cost of policing September's Whiterock parade and subsequent rioting was £3m, the police have confirmed.
Police came under sustained attack during the disturbances
They also said that damage and repairs to police vehicles over the summer period totalled £938,000.
Chief Constable Sir Hugh Orde said the costs were unacceptable not only in financial terms but in the human cost to the police and local communities.
Officers were attacked with petrol bombs and blast bombs, as well as live rounds during the trouble.
The violence started after an Orange Order march was barred from going through security gates on west Belfast's Springfield Road, and had to use a former factory site.
"My officers, as I have said before, acted like heroes in the face of the worst public disorder this police service has ever witnessed," Sir Hugh said.
"It gives us no pleasure to stand in numbers between communities who refuse to engage with each other to resolve their differences but until they do we will continue to do our job and it will continue to cost money on this scale."
Police also revealed that from 10 - 17 September 82 people were arrested, 12 weapons recovered and 93 police officers were injured.
One hundred and fifty live rounds were fired at police, 167 blast bombs were thrown at police lines, 167 vehicles were hijacked and over 1,000 petrol bombs were thrown. Police fired 216 impact rounds.
Meanwhile, police probing the disturbances have again appealed for information.
A PSNI spokesperson appealed to those involved to "come forward and to speak to police directly".
Chief Superintendent David Boultwood said the perpetrators of the violence had been clearly and extensively shown on CCTV.
"We are asking them to come forward before our officers have to knock on their doors," he said.
"I would appeal to the community to work with us to prosecute anyone involved in public disorder."
Meanwhile, two men have been charged with riotous assembly and petrol bombing relating to the trouble after the Whiterock parade.
They are expected to appear in court in Belfast on Tuesday.