The four men, whose home was found to house a vast arsenal of weapons and fascist memorabilia, beat up their neighbour on repeated occasions.
According to Catalan police, they burst the victim’s ear drum during a beating and were planning a kidnapping to extort even bigger sums of money from him.
Although the man did not report the case to Catalan police, medical staff informed local authorities when he turned up in hospital with serious injuries.
The four men, known to have ties to radical football groups, have since been arrested, Catalan daily La Vanguardia reported.
Their aim was to cover the costs of their jailed colleagues' defence, behind bars while awaiting trial for attacking a group of youths with knuckledusters and crowbars.
During the attack, which took place at an anti-fascism concert in the Catalan city of Manresa in 2012, the Nazi sympathizers injured one of their victims so badly “he would have died had he not received immediate medical help”, the court heard.