Every once in a while, maybe even every quarter of a century, football should apply a value for money test. Had it happened in this week of the Alexis Sanchez trading there would have been a particularly astounding result.
The evidence on this one, as Sanchez made his triumphant march along the gold-brick road to Manchester United, in fact stretched back just a little more than 25 years.
It was the November day in 1992 when United paid Leeds United £1.2 million for Eric Cantona. Everyone knows what United got for their money.
They got dynasty, wild controversy, brilliant understanding of what one major, if not hugely heralded, footballer could bring to the self-belief of a winning team; they got the kick of a mule and the fantasy of a dreamer.
It cost them, and no inflationary rules this side of madness can explain it, £8.8 million less than one agent sought to plunder from the Sanchez deal over the last few days.
No blame on Sanchez for this. He didn't create his world, he inherited it, though perhaps it is fair to say that just recently he has been far from diffident about its potential for huge personal profit.
Sanchez, of course, is a top player, a hard single-minded opportunist and United manager Jose Mourinho knows well enough what he is getting. It is a world-class finisher, ruthless, but, as he pushes 30, hardly the maker of a dynasty.
But then, of course, Mourinho doesn't do dynasties. He does scorched earth player psychology, he wins one year, and then perhaps a second year, and then the search is on for the dead bodies, which at Real Madrid once and Chelsea twice happened to be his own.
Mourinho needs Sanchez for a strong showing in the second half of the season, the hope of getting a little closer to Manchester City in the Premier League and some extra impact in the Champions League. He wants that certain arrogance which shapes so much of what he says and does and sometimes achieves in football and which he cultivates so relentlessly in himself.
And the cost, it just kept rising and rising this week to the point where that old Cantona deal became a relic - a shining one, no doubt, but still a relic.
United manager Alex Ferguson wasn't besotted by the potential of what many believe to have been his most influential signing.
Cantona was volatile in the extreme. He left a stream of dissension behind in a French playing career which involved six clubs in eight years, had been banned from the French national team after profoundly insulting the coach Henri Michel on national television, and it was on the initiative of Michel Platini that he moved to England to re-make himself.
Eventually Platini restored him to the French team when he was appointed coach. Ferguson simply took the lesser of some more appealing options - or so he thought.
He needed to add fire power, he chased Alan Shearer unavailingly, bid £3million for Sheffield Wednesday's David Hirst, signed Dion Dublin, who was promptly crocked.
And then one day Leeds United called Manchester United to ask if Denis Irwin was available for transfer. He wasn't but while they were on Ferguson had a passing thought on the mad Frenchman and Leeds said yes, they would sell.
They would sell a man who had an astonishing capacity to lift himself and all around him on to another level of competitive certainty. The record of the prime of his career, which came to a surprisingly early ending at the age of 31 - Ferguson was stunned when he was given the news - would have provided, without any of the dramas that came with it - a mystique of its own.
He won four league titles in his five seasons at Old Trafford - it would have probably have been five but the long suspension which followed his kung fu attack on a Crystal Palace fan - and did the double twice, once with the winning goal at Wembley.
But for his rage at Selhurst Park his last seven years would have been invincible with the title wins that came at Marseille and Leeds before he arrived at Old Trafford.
Now, as he presents himself on the film screen and boisterous TV adverts, it is maybe a little easier to understand that the disciplines of football were always going to be a challenge.
What is certain is that in a new age, and with all its rewards, Alexis Sanchez cannot seriously be expected to make anything like such impact on Old Trafford. It is hardly a slur.
According to the values of the day, Sanchez can make his stab at providing value for money. He can score a vital Champions League goal, he can give vigour and bite to the United attack, he can be valued for what he is, a genuine and highly talented competitor.
Certainly it is unlikely Sanchez will mystify any audience as profoundly or as famously as did Cantona when, after being sentenced to 120 hours of community service for his attack on the fan, explained, "When the seagulls follow the trawler it is because they think sardines will be thrown into the sea."
If so much of him was mystery, there were times when he was prepared to touch at the heart of his feelings. I once encountered him at the close of a training session near the end of his career and he was in a wistful, even poignant mood.
He said: "I love this club and this game so much that sometimes I fear how hard it will be to leave. When I go out to play I do not just play for myself and my team-mates, I play for the old players, for the memory of those who died in the Munich air crash. I play for everyone who loves this place. So, yes, sometimes I lay awake at night and think how it will be when it is over."
For Alexis Sanchez it is, of course, just beginning. However exemplary his motives, they would hardly be harmed by a brief reflection on the meaning of Eric Cantona.