One day, we might look back upon the 2019 summer transfer window and view it as a turning point. Maybe it will be the moment that clubs woke up to the reality of inflated contracts and fees, or perhaps realized that adding talent for the sake of it is only worthwhile if the price is right.

What is certain is that we have never had a summer like this, with a transfer market in which so many high-earning superstars were up for sale.

Gareth Bale, Paulo Dybala, Neymar, James Rodriguez, Christian Eriksen, Radja Nainggolan, Philippe Coutinho, Mario Mandzukic, Alexis Sanchez, Romelu Lukaku, Toby Alderweireld, Ivan Rakitic, Mauro Icardi, Emre Can, Chris Smalling, Ousmane Dembele, Danny Rose, Henrikh Mkhitaryan, Ivan Perisic, Jerome Boateng, Blaise Matuidi; the list of those available goes on.

Some moved, though all but Lukaku did so on loan: Icardi to Paris Saint-Germain, Sanchez to Inter, Smalling and Mkhitaryan to Roma, Nainggolan to Cagliari, Perisic and Coutinho to Bayern. All but the latter three moved in the final days of the transfer window, after their clubs spent much of the summer trying to offload them, but most stayed put, which begs the question: Why?

Why, at a time when Europe's top clubs are hugely profitable and enjoy a massive competitive advantage, would they not look to strengthen further? Why would clubs happily announce to the world that their employees are available for transfer, knowing that doing so would diminish their value?

Every case is different, both in terms of why a player became available and to what degree he was available, but each of the players above competed for a club that was willing to listen to offers and, in some cases, explicitly told their man that his services were no longer needed. Zinedine Zidane did it with James and Bale, Inter did it with Icardi, Perisic and Nainggolan, Manchester United with Lukau. Others were more subtle, but, still, the fact that we had so many is unprecedented.

The consensus among a number of executives interviewed was that this was a "market correction." Clubs had overextended themselves; the gap between the very richest 10 or 12 had grown so large that the biggest found themselves with excess inventory.

Gareth Bale looked certain to leave Real Madrid during the transfer window, but remains with the Bernabeu club. Josep Lago/AFP/Getty Images

"Most of the players you mention have very high wages and long contracts; they are simply beyond the budget of all but a handful of clubs," Umberto Gandini, former Roma chief executive and European Clubs Association vice president, said. "So it's a supply and demand situation."

When a factory has excess inventory, it can sell at a large discount. But a player is -- generally -- a sentient human being, not a crate of ball bearings, and as such can turn down a deal. Moreover, unlike the crate of ball bearings or, even, in another sport like the NFL, where unwanted personnel can be cut, footballers have to be paid. If he has a long-term contract and is unwilling to take a pay cut, buyers might be simply unable to afford him, even if there is a deep discount on the fee.

Gandini added: "Maybe in the past you might have had a club in the next tier down deciding to take a risk -- and it is a risk when you consider the fee, the wages, the length of contract and the reduced resale value if it's a veteran, it's a massive risk -- but with Financial Fair Play that's not going to be possible in many cases."

Indeed, FFP has created a whole cohort of clubs just below the highest echelon who have to watch their spending like never before. The heavy investment that might have once allowed a quantum leap to the top tier is no longer possible when you are dealing with "break-even requirements."

It is not a coincidence, then, that a number of moves were loans with the loaning club subsidising the move in some cases. When a team takes a player in this way, they are either not convinced they want to invest in him or they cannot afford him.

The parent club, meanwhile, gets all or part of his wages off the books, while hoping he will have a great season and someone will want him in 12 months. It's the equivalent of those infomercials where you can try the StepMaster 3000 for free at home for three months and if you are not absolutely satisfied, simply send it back. Try before you buy, as it were.

There is another element at work, as far as the biggest clubs are concerned. While you may disagree on some of the names above, there is little question that most of them, in absolute terms, would make any club better. By how much and at what cost, though?

"Those few clubs that can afford them are already very strong and, relative to the costs involved, they don't feel that another very expensive signing, especially a veteran with little resale value, will move the needle," Michael Emenalo, former Chelsea and Monaco technical director, said. "It might make them a little better, it could make no difference at all, but relative to the cost, it's not worth the risk."

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The view is echoed by Gandini.

"The biggest clubs are entertainment brands as much as they're clubs," he said. "And I think they're being more careful about how they operate. They think more carefully about how much a player adds to the club, both on the pitch and as a brand, and they put a number on it. And if they don't think they'll get a return, they don't act."

To some that might be a little chilling, but you can see the logic. Take Neymar, whose proposed transfer from Paris Saint-Germain to Barcelona fell through. He is a massive brand and a great footballer, but how much less of a brand is Barcelona (or Manchester United or Bayern Munich) without him? If that number is substantially less than what he would cost, well, you can see why potential buyers would go in another direction.

The case of Mathijs De Ligt illustrates another factor in the window that was. The Ajax defender was on the market and Juventus eventually beat Barcelona for his signature, which cost 75m Euros (around $80m). But there were other clubs that might have had a need for his services.

Manchester City and Liverpool, for example, enjoyed successful seasons, but both could have used a new central defender, given that Vincent Kompany left the former and Joel Matip had a year left on his deal at the start of the summer. Neither the Premier League nor European champions showed much interest in De Ligt, though.

Why? Possibly because both have hugely powerful and successful managers with very specific ideas about what they want. Adding De Ligt makes you more talented, sure, but it can also be disruptive to bring in a player after a season in which you gained 98 (City) and 97 points (Liverpool) and combined to win three other cup competitions.

Even if he does bring about improvement, are those clubs going to surpass last season's achievements? Probably not. And because managers are evaluated not just on results but on results relative to spending, such a massive signing, coupled with only marginal improvement (or, more likely, a step backward), is not going to help.

Emenalo cites Rodri -- by no means cheap at 70m Euros ($74m) when he moved from Atletico Madrid to Manchester City -- as the kind of signing managers such as Pep Guardiola or Jurgen Klopp are likelier to make.

"Clubs realize that you can't win everything every year and, more importantly, you don't need to win everything every year to preserve your standing as a club, the strength of your brand or the revenue you earn," Emenalo said. "If the right player comes along, who fills a specific need, then they might sign him, maybe even at great expense to get him in early. But if they are already strong and competitive, they are reluctant to go to great expense to sign even a very talented player if it means disrupting what they have. That's a relatively new phenomenon, I think."

Viewed through one lens, the "Great Correction of 2019" is a positive. Clubs are smarter about how they pay players, and are less willing to take risks and throw money around. (It is obviously due in part to Chelsea's transfer ban, but the net spend of the Premier League's six biggest clubs was the lowest it has been since 2012.)

Equally, though, if it means "doing just enough" to stay on top while also ensuring owner-investors continue to earn handsome profits, that might not sit well with everyone.

"I heard somebody say that there used to be professional clubs and amateur clubs," Gandini said. "Now we have amateur clubs, a large group of professional clubs just trying to survive and a smaller group of professional clubs who maybe have an illustrious past and are desperately trying to move to the top tier but finding it very difficult.

"And then we have the ones at the top, which aren't clubs at all, but entertainment brands," he added. "They are made up of entertainers and they act like entertainers. It may be an exaggeration, but not by much."