In the eyes of the football agent Barry McIntosh, who acts for Tranquillo Barnetta, the offer of £40,000 a week to his player was "ridiculous". There could be "no hope in hell" of the Swiss midfielder joining Newcastle United for such a derisory sum. So just over £2m a year is not enough for a perfectly decent 26-year-old who may, thanks to mundane defensive lapses, have scored with a pair of free-kicks against England at Wembley in June but who never will be mistaken for Zinedine Zidane. What a perfect mini-overture to the Premier League season.

Just when you think English football might be settling down and acquiring a sense of proportion, it all goes mad again. Or so you might conclude when told that, in order to acquire the players most coveted on the international scene, the very richest clubs are now offering salaries approaching a quarter of a million pounds a week, which is what Manchester City are paying Sergio Agüero.

Immoderate prosperity at the top has been the distinguishing feature of the Premier League since the founder members' agreement was signed 20 years ago this summer, followed by the Sky deal that began with the debut season 12 months later. Now the league's global popularity is the object of much jealousy around the world, often from formerly pre-eminent rivals who wonder where they missed out. Only Spain – whose national team hold the world and European championships, whose league boasts two teams unmatched for glamour and where players are also paid £250,000 a week – stands as a bulwark against English power.

Just look, for example, at the state of Serie A. Last week Adriano Galliani, who runs Milan on Silvio Berlusconi's behalf, told an interviewer: "Italian football has gone from a five-star restaurant to a pizzeria." A crushing enough verdict, you might think. But then Galliani delivered the final insult: "If we carry on like this, we'll even be overtaken by the French." And so they might be, given that the French league has signed an interesting television deal with al-Jazeera and Qatar Sports Investments have pumped money into Paris Saint-Germain.

"The Premier League is the best in the world and it is going to stay that way for a long time," Gérard Houllier writes in his foreword to Joe Lovejoy's Glory, Goals and Greed, an idiosyncratic survey of the past 20 years. "Why is it the best? Because of the mentality. Here, you always play to win and the entertainment comes from that." This, Houllier says, is why people on the other side of the world get up in the middle of the night to watch it. Hardly an original opinion, but we could see the truth of his words at Wembley on Sunday, where the ferociously competitive desire of Sir Alex Ferguson yet again shaped a big match, as it could be said to have shaped the entire history of the Premier League, starting with the £1m gamble on Eric Cantona.

It might be worth wondering whether such tension will continue to crackle so compellingly through the top flight of English football once Ferguson has gone. Only, perhaps, if José Mourinho takes his place. Left to themselves, Wenger, Mancini, Dalglish and Villas-Boas might struggle to maintain the box-office electricity.

But you have to wonder, too, about the future of such prosperity at a time when those further down the ladder are not so well insulated from the economic problems of the outside world. As the New York Times reported last week, the extremely rich are the last to feel the bite of a recession: in America, where 25% of all mortgage holders are in negative equity and the government borrows from China to pay its bills, the very highest end of the luxury-goods market has never looked stronger, and there are waiting lists for this season's $9,000 Chanel sequined tweed coat.

Just like the Premier League, prospering mightily while those lower down are condemned to struggle. But how long, given the levels of debt involved, can it all last? Maybe Barry McIntosh should have taken that 40 grand a week while it was on the table. And while Sir Alex is still at his desk.