The ongoing summer transfer window is a testament to the inflated football economy, as the game has witnessed a massive influx of cash over the past couple of decades. €100million-plus fees have become the new normal for transfers involving world-class talents, as ten transfers have exceeded that mark in the last five years.Whether we like it or not, the game of football has increasingly become a business over the years, which has meant that top clubs need to splurge big money on elite talent. It is no surprise that some of the most successful managers in modern football have spent enormous amounts on player recruitment in the transfer market.On that note, let's take a look at the ten highest-spending coaches since 2000.#10 Unai Emery | €846 millionUnai Emery has won Europa League titles at two different clubsUnai Emery created history in the 2020-21 season when he led Villarreal to their first major European trophy and his fourth UEFA Europa League title.The Spaniard became the most successful manager in the history of Europa League football, as he previously won three successive titles with Sevilla. Emery leapfrogged the likes of Rafael Benitez, Jose Mourinho and Diego Simeone, who have won two titles each.OFFICIAL: The top 10 nominees for the 2021 Men's Coach of the Year award:◉ Pep Guardiola◉ Roberto Mancini◉ Thomas Tuchel4️⃣ Unai Emery5️⃣ Diego Simeone6️⃣ Antonio Conte7️⃣ Gareth Southgate8️⃣ Christophe Galtier9️⃣ Ole Gunnar Solskjær🔟 Kasper Hjulmand— Squawka News (@SquawkaNews) August 19, 2021Emery has managed eight clubs since the turn of the century and has recruited 73 players, spending a cumulative total of €846 million. The 49-year-old has been at the helm of several top European clubs, including Arsenal, PSG, Valencia and Sevilla, to name a few.#9 Ernesto Valverde | €864 millionFormer Barcelona manager Ernesto ValverdeFormer Barcelona manager Ernesto Valverde has been one of the highest-spending coaches since 2000. While Valverde signed the least number of players among the other managers on our list (53), he spent a higher amount on average on each recruit.During Valverde's two-and-a-half-year stay at the club, Barcelona splurged - sometimes unwisely - on several players. This includes £160m on Philippe Coutinho from Liverpool and another £120m on Ousmane Dembele from Borussia Dortmund in Valverde's first season at the club. The Blaugrana would also sign Antoine Griezmann for £108m and Frenkie De Jong for £77.4m in Valverde's last six months at the Camp Nou.Valverde spent a combined total of €864 million in his managerial career to recruit 53 players at six different clubs.#8 Arsene Wenger | €891 millionArsene Wenger managed the Gunners for 22 yearsArsene Wenger is undoubtedly one of the greatest managers of the Premier League era and arguably one of the greatest in the history of the game.Functioning on a limited budget compared to the other top English clubs, the Frenchman established Arsenal as one of the biggest clubs in England and Europe. Currently appointed as FIFA's Director of Development, Wenger enjoyed an illustrious 22-year spell in North London. The 71-year-old recruited 84 players for the Gunners since the dawn of the century and has one of the lowest average spends among the other managers on the list.“You cannot buy success just by buying big names” - Arsene Wenger in 1996 pic.twitter.com/kaQoRAHXsc— Sky Sports Retro (@SkySportsRetro) August 19, 2021Wenger spent a total of €891 million on recruitment since 2000, spending an average of €10.6million on each player.