Sir Alex Ferguson's recent mantra has been, "There is no value in the transfer market", an explanation for his lack of spending, a defence of the Glazers' regime and an implied criticism of those who do pay what he deems excessive fees.
The Dutchman is already 29. United will not make a profit on a player who has cost £24 million (Dh138m) and who would have been available on a free transfer next summer.
In another, however, Ferguson has both confounded his critics and defeated his own argument.
No value? He has just signed the most valuable player in English football, a man who contributed 30 goals and nine assists in the league alone for Arsenal last season.
For once, Ferguson has abandoned his youthful transfer policy. For once, he is looking for an immediate impact. For once, he has bought an established world-class talent.
And now he has a forward line to savour. Think of his great United attacks - the twin warriors that were Eric Cantona and Mark Hughes, the fearsome foursome of Andrew Cole, Dwight Yorke, Teddy Sheringham and Ole Gunnar Solskjaer, the deadly trio of Wayne Rooney, Cristiano Ronaldo and Carlos Tevez - and, potentially, Van Persie and Rooney bear comparison with any.
Besides being a guarantee of goals, if £24m takes the title back to Old Trafford, it will be money well spent.