On the back of one of the most memorable transfer windows in recent memory, a number of football's top stars now have new homes. 

Lionel Messi moved to Paris Saint-Germain from Barcelona on a free transfer, while Cristiano Ronaldo cost Manchester United a very reasonable upfront fee of €15.75 million.

Elsewhere around Europe, though, there was plenty of cash spent - meaning the annual CIES Football Observatory analysis on transfer spending makes for very interesting reading.

The research - which looks at the total cost of assembling every team's playing staff in each of Europe's top five leagues - has provided us with a list of the current top 20 most expensive squads across the continent.

For comparison purposes, all prices are given in Euros and include any add-on fees that the clubs could be due to pay in the future.

Top 20 costliest squads in European football by transfer fees spent

20. Monaco (Cost of squad including add-ons -  €326m)

19. Inter Milan (€341m)

18. Borussia Dortmund (€346m)

17. Aston Villa (€351m)

16. Roma (€362m)

15. Leicester City (€411m)

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14. Napoli (€417m)

13. Bayern Munich (€421m)

12. Everton (€467m)

11. Atletico Madrid (€482m)

10. Tottenham Hotspur (€551m)

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9. Barcelona (€578m)

8. Arsenal (€630m)

7. Juventus (€657m)

6. Liverpool (€672m)

5. Chelsea (€780m)

Thomas Tuchel's side parted ways with Tammy Abraham, Kurt Zouma and Fikayo Tomori this summer for a combined total of almost €110m. However, the Blues' signing of Romelu Lukaku for in excess of €120m from Inter means that the total value of Chelsea's squad remains among the highest in Europe.

4. Real Madrid (€787m)

This figure would have been significantly higher had Los Blancos succeeded in their attempt to land Kylian Mbappe for €220m on deadline day. 

A squad featuring names like Gareth Bale, Thibaut Courtois, Ferland Mendy, Eden Hazard and Karim Benzema was expensive to assemble, though, meaning that Real still sit fairly high in this countdown.

3. PSG (€939m)

The Parisian giants pulled off a number of cracking free transfer deals during the summer transfer window. In addition to Messi, Gianluigi Donnarumma, Georginio Wijnaldum and Sergio Ramos all arrived at the Parc des Princes without a single penny being paid in transfer fees.

However, when you consider that the Ligue 1 side has Neymar (€222m) and Mbappe (€188m) in their ranks, the massive total cost of their squad won't surprise many.

Their summer recruitment of Achraf Hakimi from Inter for €63m pushed PSG's total spend close to 10 figures.

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2. Manchester United (€1,023m)

One side that has now hit that particular mark is Manchester United. The Red Devils finally secured the signature of England winger Jadon Sancho for around €90m and shortly afterwards landed Raphael Varana from Real Madrid for €42m.

When you add in the cost of bringing Ronaldo back to Old Trafford, it's been an expensive few months for United. Ole Gunnar Solskjaer doesn't quite have the most expensive squad in all of European football, but they've certainly closed the gap recently.

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1. Manchester City (€1,080m)

There's no denying that most Man City fans will consider the transfer window that has just closed to have been a disappointment. Having looked likely at certain points to land Harry Kane and United's Ronaldo, the only major arrival at the Etihad over the summer was €116m Jack Grealish from Aston Villa.

Although Pep Guardiola might not have added to his ranks in quite the way he would have wanted, City have a wealth of quality players on their books - most of which came with hefty price tags. 

Kyle Walker, John Stones, Rodri and Joao Cancelo all breached the €50m mark in terms of their transfer fees. Aymeric Laporte, Riyad Mahrez and Ruben Dias each fetched more than €60m for their former clubs.

Man City, then, are still top dogs in terms of the cost of their squad. However, neighbours and fierce rivals United are now closing the gap rapidly. It's down by €140m since last year - and might just continue to shrink over the next few seasons.

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