Monaco made an astonishing EUR289million in profit from their transfer activity in the last window, while Real Madrid and Arsenal were among the other major clubs to generate more cash than they spent.
The CIES Football Observatory has released analysis of the transfer activity in Europe's top-five leagues and found Monaco generated EUR394m in player sales, while only spending EUR105m of that on replacements.
The Ligue 1 champions allowed Kylian Mbappe, Benjamin Mendy, Tiemoue Bakayoko and Bernardo Silva to leave in lucrative deals.
Monaco's net balance would have been even higher had Thomas Lemar joined Arsenal on deadline day, Arsene Wenger having confirmed the Gunners made a EUR100m bid.
23 - Mbappé was involved in 23 league goals in 16/17 (15 goals, 8 assists), more than any other U20 player across the European Top 5. Jewel. pic.twitter.com/oP7L6nNrhj-- OptaJean (@OptaJean) August 31, 2017
Borussia Dortmund made the second biggest profit from their transfer activity, their dealings generating a positive net figure of EUR110m with Ousmane Dembele's switch to Barcelona - which could reach a value of EUR147m - the biggest contributor.
Lyon were third on the list having made EUR72m, they received EUR129m in sales including Alexandre Lacazette to Arsenal and Corentin Tolisso to Bayern Munich.
Real Madrid's frugality in the transfer market continued, as they generated revenues of EUR47m through their dealings, Alvaro Morata joining Chelsea in their highest-profile departure.
Paris Saint-Germain's world record transfer for Neymar meant they had the highest negative balance at -EUR343m, while three Premier League sides were in the top five.
Manchester United (-EUR186m), Manchester City (-EUR173m) and Chelsea (-EUR106m) were all just behind AC Milan on a negative of EUR189m.
Arsenal broke their transfer record to sign Lacazette for EUR60m, but he was the only player they paid a fee for in the window, while they made EUR86m in sales, boosted by Alex Oxlade-Chamberlain's deadline-day move to Liverpool.
Of the five leagues, LaLiga was the only league to make an overall profit on transfer activity.
Clubs in Spain's top flight cumulatively made EUR9m, but Ligue 1 lost EUR55m and the Bundesliga's net outlay was an EUR81m loss. Serie A's negative balance was EUR139m, while Premier League clubs splashed out EUR835m more than they received.