The four suicide bombers who killed 52 people in July spent less than 1,200 pounds (about US$2,000 or euro1,700) on staging the attacks, security experts said Tuesday.
The cost was far less than that for similar attacks - about one-fifth of the estimated US$10,000 (euro8,500) needed for the Madrid train bombings in March 2004, independent defense and security expert Paul Beaver told The Associated Press.
"I think the London bombings, including buying the train tickets and conducting reconnaissance, were done for no more than 1,200 (pounds)," Beaver said. "You can buy the ingredients they used ... without arousing any suspicion."
London police have said the four men used inexpensive, peroxide-based explosives, but they declined Tuesday to offer a figure until they had completed the investigation into the "wider circumstances of how the attack was funded."
Earlier Tuesday, the British Broadcasting Corp. said investigators believe Mohammad Sidique Khan, 30, was the group's chief's financier. Khan, who worked as a teaching assistant, appeared to have had access to the most money among the four suspect bombers.
Khan died in the attacks along with the other three suspected bombers: Hasib Hussain, an unemployed 18-year-old; Germaine Lindsey, 19, and Shehzad Tanweer, 22, who helped out at his family's fish and chip shop.
Loretta Napoleoni, an expert on financing terrorism, also backed the notion that the bombings were less expensive than earlier attacks - largely because the bombers were homegrown, all living at home and traveling to the capital using a rental car and a train.
"They were just a group of friends who lived at home," she said. "Their only costs were the homemade explosives and the traveling costs to London. It did not involve anything else."
Other costs, however, may have been incurred in any training they received.
Within days of the July 7 bombings, British Treasury chief Gordon Brown urged his European counterparts to work more effectively to stop the financing of terrorism.
"There should not only be no safe haven for terrorists, but their should be no hiding place for terrorist finance. Our aim is to cut off the source of terrorist finance. We believe one of the ways we can get to terrorists is by investigating financial transactions that are supporting them," Brown said, days after the bombings.
But a U.N. report released in August 2004 revealed that sanctions and other measures taken to prevent funding to al-Qaida had only "limited impact" in preventing terrorist attacks.
The report said the group's worldwide bombing campaigns were carried out relatively cheaply. It said that al-Qaida has spent less than US$50,000 (euro42,000) on each of its major attacks since the Sept. 11.
The low cost allegedly involved in the London bombings indicated that terrorism had evolved from the Sept. 11 attacks, with each attack costing less.
"This is part of a pattern," she said. "What a lot of the new groups are doing is taking 9/11 as a blueprint and applying it to whatever their financial circumstances are."
Magnus Ranstorp, terrorism expert and research director at the Center for Asymmetric Threat Studies in Sweden, acknowledged the money needed to carry out attacks has fallen consistently since the Sept 11 attacks on the World Trade Center, but says the benefit of investigating terrorist finances should not be underestimated.
"If the terrorists are lillywhites - or not known to the authorities - and their planning process is well executed, then I would say there is no problem of them launching a successful attack," he said in a telephone interview.
"Trying to stop terrorism through tracing and constricting financing is not going to be a panacea. But you cannot discount it. It's one way you can prove involvement by detecting elicit transactions and get an insight into how networks are changing."