Chelsea reportedly paid £21.5m to hire Graham Potter as the club's head coach.
Potter spent three years in charge of Brighton & Hove Albion, before he was appointed Chelsea boss last September.
The Englishman was chosen as Thomas Tuchel's successor ahead of the likes of Mauricio Pochettino and Ruben Amorim.
Potter, who signed a five-year contract with the Blues, took several members of his Brighton backroom staff with him to Stamford Bridge, including Bjorn Hamberg, Billy Reid, Bruno Saltor and Kyle Macaulay.
The cost of appointing Potter has now been revealed after Brighton & Hove Albion published their 2022-23 accounts.
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Brighton's accounts state: "On 8 September 2022 the club was delighted to appoint Roberto de Zerbi as its new Head Coach following the loss of Graham Potter and his team to Chelsea a few days earlier in a deal that saw the club receive a sum of £21.5m."
According to football.london around £20m was splashed out on Potter, while the remaining amount was spent on his backroom staff.
Potter's tenure as Chelsea boss began with a nine-game unbeaten run in all competitions, before the Blues were beaten 4-1 by Brighton in October.
The Chelsea head coach has since seen his position come under question after beginning 2023 with one win in 11 games across all competitions.
However, three consecutive victories - including a 2-0 second-leg win over Borussia Dortmund to progress to the Champions League quarter-finals - relieved some of the pressure that was building on the 47-year-old.
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Potter would have been left frustrated by Saturday's result though, as Chelsea conceded a late goal to draw 2-2 at home with Everton.
Brighton's accounts also reveal that Chelsea paid over £60m to sign Marc Cucurella from the Seagulls last summer.
The Blues also made £10m from loaning defender Levi Colwill and selling midfielder Billy Gilmour to the South coast side.
Chelsea, who occupy 10th position in the Premier League table, will return from the international break with a home game against Aston Villa on April 1.
