|Ilyas and Tallat Ashar from Eccles were jailed in October last year|
Ilyas and Tallat Ashar were jailed last October after the girl was found in their cellar in 2009.
The victim was repeatedly raped and forced to work as a servant at the family's properties as a child.
Manchester Crown Court ruled the couple must also repay £42,000 of benefits falsely claimed in her name.
The Ashars must also pay £321,000 towards the cost of their trials.
Now in her 20s, the victim, who cannot be named, is believed to have been as young as 10 when she was trafficked into the UK.
The girl was found in a cellar in 2009
Police said the victim's details were used on bank accounts linked to the couple.
But when officers tried to speak to her at the house, they realised she was incapable of communication and moved her to a place of safety.
Police said she could not read or write, and have accepted that benefit fraud was carried out by the Ashars.
The victim had to learn a form of sign language to give evidence at the trial last year, when her progress was compared to "a butterfly coming out of a chrysalis".
She is now living independently and has improved her sign language skills, said police.
Analysis: Stuart Flinders, North West Tonight
This was a hearing under the Proceeds of Crime Act - legislation normally used to confiscate the houses and big cars of drug dealers.
It is believed to be the first time it's been used in a case of modern slavery.
The court had to calculate the value of the work carried out by the girl when she was being exploited and also the sum of benefits claimed fraudulently in her name.
The judge based it on the minimum wage, assuming she worked for 12 hours a day, seven days a week.
Lawyers for the couple argued a deduction should be made for board and lodging accrued by the girl when she was with them.
But the judge said that would be akin to allowing a drug dealer to claim for a fuel allowance while drugs were being delivered.
The judge made it clear that it was not about whether the couple benefited from their crimes but of putting a price on it.
During their trial last year, Ilyas Ashar, 85, was found guilty of 13 counts of raping the girl.
He and his wife, Tallat Ashar, 69, were both convicted of benefit fraud and trafficking.
The Court of Appeal extended their jail terms to 15 years and six years respectively this February, after the pair's sentencing last year was described as "unduly lenient". Originally, they were sentenced to 13 years and 5 years respectively.
The couple's daughter, Faaiza Ashar, 47, was given a 12-month community order with 300 hours of unpaid work after she was also found guilty of benefit fraud.
Ch Supt Mary Doyle, from Greater Manchester Police (GMP), said: "Today's result is a landmark case for both GMP and for victims of trafficking everywhere.
"The crimes of the Ashars are well-documented and, quite rightly, people continue to share a sense of disbelief at the prolonged cruelty they inflicted on their young victim."
She added: "The money will in no way make up for what she went through over a number of years, but it will help her move on with her life and continue her inspiring recovery from these awful events." This is so good to read that she is recovering well. God bless her.
The Proceeds of Crime Act hearing ruled Ilyas and Tallat Ashar have six months to pay back a total of £41,968 they gained through benefit fraud.
If they fail to repay in that time, they could each be imprisoned for a further two years.