London, May 23 : Austrian incest fiend Josef Fritzl freed three of his kids from their dungeon so that he could get 2,000 pounds a month as child benefit.

The 73-year-old told cops that he showed mercy because the prison was too small for the six children he fathered over 24 years with sex-slave daughter Elisabeth, 42.

But cops say he raked in around 480 pounds for Lisa, now 15, after she was adopted.

He also got 800 pounds each for Monika, 14 and Alexander, 12, who lived as foster kids upstairs with him and wife Rosemarie.

“They were cash cows for him,” The Sun quoted an investigator, as saying.

“Everything he did was not out of concern for them, but to get money,” the investigator added. (ANI)