The family moved into the property in July
A woman is receiving more than £12,000 a month in housing benefits so she and her children can live in a seven-bedroom house in west London.
The woman, who is from Afghanistan, approached Ealing Council in July when she and her children became homeless.
They were placed in a privately-owned seven-bedroom house off Horn Lane, Acton, as the council had no properties that size.
The authority said it has a legal obligation to help them.
Following changes in the law, the council was forced to pay well over the average market rate for the property.
Local lettings agent Rajesh Kathuria, from RSK Homes, said the average rent commanded for a seven-bedroom property on the road would be between £2,000 to £2,500 a month.
"That should be quite a reasonable price according to my experience," he said.
Jawad Saindi, one of the sons, said the family were pleased with their new home.
"I think the property value is quite high, basically we were lucky to get this house," he said.
A council spokesman said the case exposed the "absurdities" of the housing and benefits system.
"The sums of money involved in this case will offend people's feelings of 'fair play', especially as so many are having difficulties paying bills at the moment," said Councillor Will Brooks.
"The story highlights some of the absurdities of the housing and benefit system. "
In April, the government introduced the Local Housing Allowance (LHA) which established national rules about what type of accommodation is appropriate and how much rent can be paid to landlords.
The change enables tenants and landlords to find out the maximum amount of LHA available before an agreement is reached.
"We believe that urgent changes are needed to the LHA and in particular for the publication of maximum rent levels to be ended," said Mr Brooks.
"This would enable all councils to be able to negotiate more competitive rent agreements without being undermined."
The Rent Service - an executive agency of the Department for Work and Pensions (DWP) - advised that the council pay the landlord £12,500 a month, partly because under boundary changes Acton is placed in the same category as the more affluent area of Westminster.
A spokeswoman for the DWP said: "This is quite an extreme case. This is one of probably only a handful of cases like this particular to London."
She said the government were currently reviewing the boundaries.