The Red Devils signed the Dutchman from Arsenal for a hefty £24m, despite the Netherlands striker being in the final year of his contract at The Emirates.
Ferguson’s faith in the 29-year-old has been instantly repaid with a return of 20 goals in 26 appearances in all competitions so far this season.
And although the Manchester United boss admits the transfer fee was high given Van Persie’s contractual situation at Arsenal, the Scot says the Red Devils were prepared to splash the cash because they wanted to sign him so badly.
“It was a lot of money for a player in the last year of his contract,” said Ferguson of Van Persie, who was named Premier League player of the month for December.
“But the thing about it is – as it proved with Manchester City the year before when they paid £24m for Samir Nasri – you either want him or you don’t.
“You have to pay the price that the club are sticking out for, whether it is one year on his contract, two or three.
“We wanted him badly, so we were prepared to go the extra mile.”
Manchester United host Liverpool in the Premier League on Sunday afternoon.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news