With a patchy injury record and only one year remaining on his contract, Van Persie looked to be something of a risk for the Manchester United manager this summer. Now the 29-year-old looks like a bargain. With 20 goals and a growing number of assists, Van Persie is in line to emulate Cristiano Ronaldo as a back-to-back PFA Player of the Year and is one of the major reasons why United head into Sunday's encounter with Liverpool holding a seven-point advantage over major rivals Manchester City. And it is all thanks to Ferguson deciding Van Persie was the man to turn United from runners-up back into champions once more.
"The first thing we look at is the player's ability," said Ferguson. "It was a lot of money for a player in the last year of his contract.
"But the thing about it is - as it proved with Manchester City the year before when they paid £24million 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.
"Any player coming to us for the first year, you never know for sure. Who would have thought Wayne Rooney would have got a hat-trick on his debut? It is fairytale stuff.
"But what we did know was that we were signing a very good player."
After his supreme goal at West Ham last Saturday, Van Persie will return to United's starting line-up against Liverpool. Wayne Rooney will not be involved though, despite reports that the former Everton man is desperate to play after his recent knee injury.
"He is not far away," said Ferguson. "I don't think it is an issue of guiding him along in terms of the injury he had. It is quite straightforward.
"If he starts training today, we should have him available for Wednesday's (FA Cup) replay against West Ham."
There is some good news on the injury front though, with Nani and Anderson both back in training after their respective hamstring problems meaning the pair are in contention for Sunday's game.
"It is Liverpool," said Ferguson.
"A derby game. That never changes. "It is always an immensely important game. "It is intense and emotional. Everything you can think of in a derby game will probably be there on Sunday."