Two years ago the figure reached $6billion, a record produced in the wake of heightened global terrorism fears and the blanket security required by the Athens Olympics and Euro 2004.
Today some 200 practitioners will gather for the summit at the Queen Elizabeth II Conference Centre in Westminster.
As well as being a talking shop for those with experience of masterminding security at the Olympics, providing VIP protection and gathering intelligence, the conference will provide a showcase for the latest technological innovations.
The summit will examine the increasingly sophisticated methods that are being used for assessing threat and risk, developing effective security strategies and coordinating agencies including police, government departments and safety officials.
The Athens Olympics passed off without any significant security breach - but that, say experts, was the result of the most complex, exhaustive and costly intelligence and security operation yet mounted. The bill spiralled to $4billion.
In its Olympics bid London allocated more than £200million for security around the 2012 Games but that is expected to rise, particularly after the terrorist attacks in the capital in July.
Kevin Roberts, editorial director at SportBusiness Group, said: "London is very much a 52-weeks-a-year sports city. Few cities in the world have five or six big professional football games played each weekend, which might coincide with a rugby international and other big events. It has to be helpful that the Metropolitan Police and London 2012 have worked in an environment where security [is] already uppermost in their minds."
